How to re-charge a/c system?????

Can someone tell me how difficult it is to re-charge your air conditioner unit?? I have a 1994 Chevy Corsica......I see a red cap on the top, and a black one on the bottom. Do you just buy the refrigerant, and the kit to make sure the fittings are right, and just fill it kinda like the fix-a flat stuff.......from the top, red cap??????Thanks in advance guys!!!! Lindsey

Oh "Shot"!! It's using R13 or R135 ?? You should recharge it from the bottom "Black hole" . And you may get caught by the "Driving belt"
Crazy Car to get your A/C recharge!! I need to recharge mine every year,and it's not cheap...GM will charge you close to $100 a pop !!!