You would need the 134A refrigerent. There is a valve sort of like a large tire valve on your AC line. Just unscrew the cap, connect the hose for the refrigerent, empty can into the system. It's bascially that easy. Walmart seems to have the best selection. There are multiple cans, some come with a hose attached, some have a hose and pressure gauge, some come as a kit with a detachable hose with pressure gauge and a can. Then you have different types of additives you can get with the 134A, some have a red dye to identify leaks, others have UV dye, others come with a charge of oil, and others come with something that is supposed to clean out the system.
I would recommend getting the packaged kit that has the detachable hose with the pressure guage. Otherwise you are just guessing on if you have too much or too little in the system. Then if you do have a leak and need to recharge it you can just get the cheap 134A bottle and fill it back up.
I've been fighting my AC compressor, it went out so I replaced it but couldn't get it to seal tight. I've used pretty much every type of refrigerent out there and the packaged kit is the best deal and most flexible.