Check that the A/C system is actually low on refrigerant
Identify the correct refrigerant type from the under-hood label
Gather the proper recharge kit, gauge, and safety gear
Park the car on a level surface and turn the engine off
Locate the low-pressure service port
Attach the recharge hose to the low-pressure port
Start the engine and set the A/C to max cold and high fan
Read the pressure on the gauge
Add refrigerant slowly in short bursts
Recheck the gauge between bursts
Stop when the pressure reaches the recommended range
Remove the hose from the service port
Replace the port cap
Test the A/C for cold air
Stop if the system will not hold charge or cool properly