1989 Buick Regal adding freon

Take a look at the how does it work section on the left side, check the a/c section it explains how the system works and general location of compodents. Freon is installed on the low end of the system. There are recharfing kits that are availanle in most auto stores. Remember that fron is under pressure especially on the high side so be careful if installing freon yourself.