The compressor is at the front of the engine, third pulley from the top, below the power steering pump and the waterpump. Most diagrams show the system w/o the compressor, but there is one in Ch. 1 of the Haynes manual.
Recharge through the low-pressure port, which has a cap that sticks up behind the radiator, near the battery. It is best to stay away from the high-pressure port behind the grille, because of the likelihood of injury if the refrigerant should erupt from that side of the system. NEVER try to connect a recharge kit to the high-pressure port. BAD things will happen.
Doing minor A/C service is easy, but I usually use a pair of cotton gloves and safety glasses to recharge or test the pressure, just in case.
Auto part stores sell recharge kits which are basically a hose with two connections and a gauge in the middle. (example, Napa # BK 7652982)
R134a refrigerant, PAG-100 oil (NG900/Seiko-Seiki compressor) PAG-46 oil (9-3/Sanden compressor)
The engine should be running, A/C at the lowest setting and doors or windows open to recharge the A/C system. The ACC on cars that have it should read "LO" while charging.
One end of the charging hose snaps over the low pressure port.
The other end of the hose screws down tight on top of the refrigerant container. The thumb screw at the container is screwed in to pierce the container seal, and then backed off to allow the refrigerant or the esther oil out.
If adding oil, the can is held upside down. If adding refrigerant, right side up.
The pressure gauge is used to monitor the low-side pressure in the system while charging. It takes a few minutes to charge the A/C system on my car, much longer than I am used to on other cars.
As the system cycles and draws the refrigerant from the can, the pressure fluctuates. It goes up when the compressor is off, and down when the compressor turns on and fluid is drawn from the can. The container will get cold and frost may form on the outside as the pressure inside drops. If the container does not get cold, it is not charging. An empty container will feel noticably lighter than a full one.
The pressure readings depend on the outside temperature (higher with higher ambient temp). The kit should include a chart of full pressure v. temperature as a guide to when to stop charging the system.
When the system reaches full pressure, the connector at the low-pressure port can simply be disconnected, and the port will seal automatically. A small amount of refrigerant may escape, and should be wiped off before replacing the cap.