Can I just cut the black wires coming out of old switch and connect with wire nuts to black wires of new switch? And cap off the ground wire from new switch since no ground on old switch?

This is much simpler than it sounds, but if you're a total novice you'll need to read it all.

First, make sure power to fixture is off. Best method is to locate circuit breaker or fuse that controls that fixture's power. At minimum shut off the wall switch to it if there is one.

Next, remove the old fixture. Usually there are two screws or decorative nuts holding the base cover (canopy) on. On ceiling pendant fixtures there may be a retaining ring holding up the canopy, unscrew this ring counterclockwise and the canopy will drop over the support chain, exposing the junction box where the wires are connected.

It is critical at this point that the power is off.

Modern house wiring and fixtures are connected with three wires.
Green or bare copper = ground (earth)
White or grey = neutral
Black, Red, Blue or any other solid color other than green, white or grey = power or hot wire (this is the wire that is controlled by a switch.
For simplicity I will call the three: Green, White and Black.

The next step requires you to carefully pull the wires out of the junction box and isolate the black, white and green wire connections from each other. Make sure the connectors (wire nuts) for each connection are accessible.

Warning: With old or over heated wiring, take extra care not to crack or disturb the insulation(wire covering) on any of the wires. If insulation is crumbling away exposing bare wire, stop and call an electrician! Do not turn the power back on until he has repaired those damaged wires, they could start a fire.

Isolate the connection between the black house wire and black fixture wire. Remove this wire nut. At this point I usually use an electrical tester to double check that the power is off by touching one side to the newly exposed black connection and any grounded metal part nearby.
(Note: some multiple switched (three way) circuits may use a white wire as a power wire. If the black fixture wire is connected to a white house wire, mark that white house wire with black electrical tape for future identification.)
Once you are positive there is no power at the fixture junction box remove the connectors from the white and green wires.

Detach the old fixture and it's mounting bracket.

Re-attach the new fixture using bracket and new connectors that are usually provided. Some brackets have a green ground screw. Wrap the bare ground wire clockwise around that screw and tighten it down leaving enough remaining ground wire to attach to the fixture ground.

If the wires to the new fixtures do not have a 1/2 inch of exposed bare wire at the ends (stripped) you must do so. I use a wire stripping tool but you can do it with a sharp knife being careful not to nick the metal wire.
Once the wire tips are stripped, hold the tips of each color pair together side by side, slip the wire nut over them and twist clockwise until snug. (White to white, black to black etc.)
Take care that the new wire nuts are secure at each connection. Do not over tighten them but insure that they are correctly attached by gently tugging on each wire. When completed the black and white connections should have no exposed bare wire showing.
The Green (bare copper) wire is there for safety and never carries current, hence exposed wire is not an issue on ground wires.

Assemble and attach the new fixture according to instructions in the box.

Pendant ceiling fixtures usually require additional assembly steps including adjusting chain height, looping wires through the chain and slipping retaining nut and canopy over chain prior to connecting. Always follow directions that come with the fixtures.

When in doubt, call a professional. Electricity is dangerous.

Add another line to 120V switch.
To begin, inside your switch box, there must be at least two cables.
Each cable has a black-wire and white-wire and bare ground wire.

If your box has only one cable, then you cannot use that for your junction.

OK, your box has 2 cables.
One cable comes from circuit breaker box. These are called Line wires. There is a Black Hot and White Neutral.
The other cable goes to light. These are called Load wires.

You are going to add a new cable with a black-wire and white-wire

In back of box, the white wires are twisted together and covered with wire nut.
These white wires are called Neutrals.
Add your new white wire to these other white wires.

The switch has 2 black wires. One black wire is the Hot line wire.
Add your new black wire to the switch screw that has the Hot.
Of course the switch has 2 black wires, so how do you know which is the Hot.
Turn light switch off, turn power ON, and test each black wire to bare ground wire.
Tester lights up on the Hot.

Review:
New white wire connects to other white wires that are twisted together and covered with wire nut.
New black wire connects to Hot wire.
Ground wires are connected together.

On your new receptacle, the black wire connects to brass screw, and white wire connects to silver screw.
Screws are color-coded to tell electrician how to wire.
http://waterheatertimer.org/Color-codewire.html
http://waterheatertimer.org/B220C.html
http://waterheatertimer.org/See-inside-main-breaker-box.html

What timer are you installing?

Intermatic battery-operated timer with red, blue, black and green
Green connects to bare ground
Red is capped off.
Blue connects to one wire
Black connects to other wire
Push on-off button: if light comes on, timer wiring is correct.
If light does not come on, then reverse blue and black wires.

Other in-wall timers except Aube have red, black, white and green
Green goes to bare ground
Red connects to one wire
Black connects to other wire.
White: in back of electrical box are white wires twisted together and covered with wire nut. Connect white white to these other white wires.
If box does not have white wires described above, then connect white wire to bare ground along with green wire.
Push on-off or override switch: if light comes on, timer wiring is correct.
If light does not come on, then reverse red and black wires.

I've tested these timers.
Here's what to do:
1) Connect green to bare copper
2) Switch has 2 wires. For now, connect these two wires to timer-black and timer-red. Choose either one.
3) In back of wall box are white neutral wires twisted together and covered with wire nut. Timer-white wire connects to these white neutral wires. This action gives power to time clock.
4) If wall box does not have white neutrals described above, then connect timer-white to bare ground wire. Bare ground connects to neutral busbar in breaker box.
5) Turn on power and click manual override button or switch. If lights turn on, timer is wired correctly. If lights do not turn on, then reverse timer-red and timer-black wires.

Manual for GE 15265
http://waterheatertimer.org/pdf/GE-15265-manual.pdf
15A timer works fine on two bulbs, up to 1440 total watts.

If old switch has 2 screws plus green ground screw, then timer is right.
If old switch has 3 screws plus green ground screw, 15265 doesn't replace 3-way switch.

Timer-green wire connects to bare ground wire

Old switch has 2 screws with wires on each.
One wire is Hot-from breaker and this connects to timer-black wire.
One wire Goes-to-lights and this connects to timer-red wire.
If you get these two wires reversed, timer will not work, so reverse them.
It will not blow circuit if the timer-red and timer-black wires are reversed.

Timer-White wire is the confusing wire for everybody:
Timer-white wire runs clock motor located inside timer.
In back of electric box are neutral white wires that are twisted together and covered with wire nut.
Connect timer-white to these neutral wires.
If box does not have neutral white wires, connect timer-white to bare ground wire.

Thank you for the clear description of your P&S device.
You need to test your wires.
We are looking for the Hot, Neutral and Load wires.

Your old switch has two wires.
One of these wires is the Hot (I suspect 100% that the wire that comes from the other wires that are twisted together is the Hot)
The other is Load

Separate the old switch wires and turn on power.
Use ordinary tester.
Test each wire to metal box and see if the box is grounded.
Tester will light up on Hot wire.
You can also test each of the old switch wires to the other wires in the box.

1) Hot: Once you determine the Hot wire, this wire will connect to the P&S device:
Hot connects to the brass screws on right side, just as you said ... and these screws are on opposite side from silver screw.

2) Load: The wire to Load connects to brass screw on top left, which is on same side of device as silver screw. This screw sits opposite the P&S switch.

The last wire is the Neutral.
Test your Hot wire to all other wires in the box.
When the tester lights up, that is the Neutral

3) Neutral connects to silver screw which will complete the circuit to the P&S receptacle.

http://waterheatertimer.org/How-to-select-right-wire-nut.html

The timer should have red, black,blue and green wires. (no white?) If you have only the two black wires coming from junction box, then connect green to ground like you did. Connect the incoming black (HOT) to the black wire on the timer.connect the outgoing (to the light) to the blue wire on the timer. Cap of with wire nut the red wire. This is for a single pole switch installation (Only switch for the light) If this is for a 3-way control (where you have 2 or more switches) then you use the red.

Hello. The red and the black are the hot wires. Therefore, connect one of your conductors to the red and the other conductor to the black. Use wirenuts. The bare ground wire should be solidly attached to the new unit's green wire using a wire nut.
Regards, Joe
PS: please rate my answer. Thank you.

I'm going to guide you on how to create what is known as a "switch leg".
1- run a 12-2 w/ground wire to the light fixture from new switch.
2- connect black wire "hot wire" to the shiny bronze tinted terminal on switch.
3- connect the white wire " neutral " to the silver connection on switch.
4- connect the naked copper wire " ground " to the ground terminal on switch
5- Disconnect the two white wires in the junction box from each other.
6- Connect the ground to ground in j-box
7- Connect the black to one of the whites in j-box
8- connect the white to the other white in j-box
9- wire nut and tape all connections
Oh and be sure that you turn off the breaker before you start. Hope this helps. Good luck.

Wiring a bathroom combination vent, heater, light 3 way switch means more wires. In brief, you need to run two cables - one a two wire and one a three wire from the switch to the fan.

Incoming power will have white black and ground.

The two wire cable for the switch to the fan will have wht, blk, and ground.

The three wire will have red, blk, wht, and grnd.

The switch will likely have 2 blacks and a red coming from it, with two blacks and a red on one side, and a single black on the other.

The fan should have a red, blue, green, black, and white.

On the fan end: Group all green/copper grounds together and use a wire nut to fasten them together. Tape the nut to the wires.
There will be five white wires coming through. For ease of handling, using wire nuts, connect two on one nut and three on the other.
connect the blue to a blck. Connect one red to one black, and the other red to the other black.

The switch will have one red going into the 3 wire cable, a black going to the 3 wire cable, and a black form incoming power to the side opposite the 3 wires, and a blck going to the two wire cable.

There. Confused?