The low-pressure side for recharging the AC system is typically located on the smaller diameter hose, near the front of the vehicle, often near the condenser (the larger, black, often finned component). It will have a service port with a schrader valve (similar to a tire valve) capped with a dust cap. This port is usually connected to the accumulator/receiver-dryer. Look for a smaller hose going to the receiver/dryer. The service port is almost always on that hose.
Caution: It's crucial to visually inspect the system for leaks *before* recharging. Simply adding refrigerant to a leaking system is wasteful and ineffective. Improperly handling refrigerants can be dangerous. If you're not comfortable performing this task yourself, it is recommended to take your vehicle to a qualified automotive technician.
