How do I recharge the AC on a 2012 Ford Focus?
If the system is low or empty of refrigerant, you probably have a leak. Take the vehicle to the professionals for diagnoses and repair.
The black or silver can is the accumulator/drier, located near the firewall on the pass anger side. It has two AC hoses connected to it and a low side recharge port with a dust cap on it. Remove the dust cap (if it is still present) and connect your recharge kit to the port. When done replace the cap.