HOW: Place your affected arm on a high surface like a countertop to the side of you. Let your shoulder completely relax. Either step out away from the table or move your hips away from the table or both, to slowly increase the amount of stretch in your shoulder.
FEEL: If you are doing this after surgery, it is normal for this to feel a bit uncomfortable. There should never be any sharp pain, but aching is fine.
COMPENSATION: Relax! If it's more comfortable to put your elbow on the high surface then do that instead of your hand.