Caution: this move can make you pass out.
Rear Naked Choke is properly executed while you are positioned at your opponent backside and goes as follows: 1. with your chest to their back place your left arm completey over their left should and against their neck with your palm facing up, 2. place your right arm around their next under their chin until your right hand is cupping your left bicep, 3. finally, lock your your hand by bringing your left hand back until your left hand is cupping the back of your opponents head.