I'd like to know how to install the dimmer to light switch.

The dimmer switch you select will depend on the type of bulbs you will be using. The 'original type ' of dimmer works with regular incandescent bulbs and halogen bulbs only. They cost around $15.00. Then there are dimmers for compact florescent (cfl) bulbs and LED lights that are dimmable, as well for regular light bulbs. These types of dimmers are more expensive, ranging in price form around $40.00 upwards.
Light Switches Dimmers

If you are replacing a single pole switch ( just one switch that operates lights) you'll need a single pole dimmer. If you are replacing a 3-way switch ( two switches that operate the same light) you'll need a 3-way dimmer.
Installing the dimmer is pretty straight forward. All dimmers come with installation instructions. Make sure you turn off the circuit breaker for the particular switch you are replacing.

Hi Frederick,

I'm an electrician and would like to help you solve this problem. I have several questions to ask to help narrow down the cause.

Is this switch installed in the same box as another dimmer switch?

Did you need to modify the heat sync fins to fit the switch into the box?

Was this dimmer recently installed to replace a switch or old dimmer? If so, what was there before?

How many bulbs and their correscponding wattage and type (incandescent, compact fluorescent, etc.) are being controlled by the dimmer?

Is there any non-lighting load connected (paddle fan, etc.)?

Can you provide the dimmer manufacturer's name & model of the dimmer? You said you have a "2 way" dimmer and there is no such beast - I suspect that you have a 3 way dimmer.

Without answers to the above - I suspect either an excessive heat issue due to overloading or ganging of several dimmers in one large box or improper use of the dimmer controlling a motor or other non-lighting or non-dimmable load.

Leave a comment with the answers and I can help pinpoint the problem.

Your question has two switches and 1 dimmer.
The fan switch works.
The light switch works.
The dimmer does not. What is the dimmer connected to?
Dimmers typically will not control fan speed unless they are rated to do that.
Do you have a 3-way switching where two switches control same light, and you installed the dimmer in place of 3-way switch?

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

As a general rule, grounding will not affect operation of dimmer.
Type of dimmer, type of switch being replaced, type of load, and how you connect wires will affect dimmer.

Here is Lutron dimmer switch page
http://www.lutron.com/Products/StandAloneControls/Dimmers-Switches/Pages/DimmersSwitches.aspx

What is the load? Are you wiring dimmer to a ballast? Or fan? Or incandescent lights? Or florescent lights?
Are you replacing a 2-way or 3-way switch?
What color are your dimmer wires?
How many wires were connected to switch?
Can you re-install the switch, and know where each wire went?
Did you replace a light with a fan, and then want the dimmer to slow the fan? Not every dimmer will work with a fan, or florescent lights.
Dimmers cannot dim LED lights.

If I know what type switch you are replacing, and the type of load you want to control, and the specific dimmer you have, I can answer the question.

You cannot, at least not using the dimmer you have in your hand. The switch with all the wires is a four-way switch, which is used to make a "suicided" 3-way switch. The power comes in AND goes out to the light from that switch. The other switch is a 3-way. Neither one has the "ON" or "OFF" marks on them, do they? You can buy a 3-way dimmer, but i do not know if rotary-style 3-way switches exist. You will have to install the dimmer at the other switch because i am quite certain no 4-way dimmers are available.

That red wire is hot, it's used in what is called a 'switch loop'. That's where the electrician will bring the hot for the circuit to the light first, then run down to the switch and back with the switched hot for the light. Turn the breaker off!

If you need further help, I’m available over the phone at https://www.6ya.com/expert/craig_3fa289bf857b1a3c

the light on the switch does not men it is wired correctly, it only means that you have supplied power at that point. Without knowing more its hard to say, but I'll assume this is a single switch operating a single unit. That being the case, and depending on your fixture, occassionally wires must be grouped together on the switch side. Also quite often these switches are simply defective, and must be returned. If you think you have it correct then its probably a bad switch.

I have found that 3-way switches must be of the same brand. Replacing the switch with a like 3-way dimmer should solve your problem. I know, they're pricey. If this solves your problem, please rate me.

florecent bulbs wont dim unless they are dimmable.

What sort of light is it , dimmer switches normally only work on Incandescent type lights not flourescent type.

Otherwise it sounds as if the dimmer function is faulty.