How do you recharge the ac on a 1999 Buick Century?

Buy a recharge kit and a # 134 refrigerant; follow directions. If the system is low, the compressor will not start so you will need to remove the connector on the pressure switch which is located on the dryer. The dryer is the silver cylinder on the passenger side. There are two metal prongs that you can jump across with a wire or pliers while your recharge kit is hooked up and soon the system will take a charge ;then you can plug in the low pressure switch and the system will work again.