Answer:
To refill a paintball tank, you must first go to a paintball field or store with a paintball air compressor. You can't refill them with just any home depot compressor, it takes serious pressure to fill these tanks. Find the fill station with the same pressure as your tank (3000, 4500 or 5000 psi) and hook up the fill hose to the fill nipple on the side of the tank while it is attached to your gun. Then press the lever or button in until the gauge on your tank or on the filler is at the correct pressure and release. Then unhook the fill hose.