My air conditioner is blowing hot air, where is the port so that I can add refridgerant?

Sounds like a bad compressor. If you have manifold gauges and the necessary tools (like a vacuum pump, Refridgerant, etc.) you can draw down the system and re-charge. But first I would take a high and low side reading to see if all is well with that compressor.

compressor bad or leaked out refridgerant

Yes you can add freon, the port will be on the line up at the accumlator tank (large silver tank on pass side close to the fire wall - will have a large black cap, does not look like a port) Get you a large can with a hose attached do not use it all save some for next year. 

Could be a number of things...electrical connections causing the compressor not to run. Turn on AC and turn your thermostat all the way to cool...now visually check to see if compressor is engaged and not just free wheeling. Most likely you lost your refridgerant due to leak in the system...would need to find leak and repair then have your system re-charged with refridgerant. Best case scenario...your system just needs a charge of refridgerant due to not having enough.

this can be a few different things going on. 1. does the clutch on your compressor engage when a/c is turned on? If so, does it cycle on and off constantely? If its cycling, your low on refridgerant, which indicates that theres a leak. System needs to be checked by professional. If compressor stays on, and you got hot air, it indicates that the problem is with the heater control valve. Normally, this can be found connected to one of the heater hoses located on passengerside engine compartment. It might be electronic, or vacuum operated.

half can is low, possible cause is that fill port is clogged happens when u put sealer in sometimes, but it sounds like your system is under charged check pressure, if no reading port is clogged change port, low reading add freon,

There are a few different possibilities for a vehicle doing this. A low refridgerant level can, or a temp control on the dash is not operating properly.

The car should have R134 freon (and should have a label in the engine compartment indicating so). R134 ports are two different sizes and your charge hose should only fit the correct port

you need to recharce your air conditioner system with refridgerant. you may have a small leak that depletes the system over time.

check too se if cooling fan is operating