This is an advanced version of a normal arm lock from inside closed guard. Instead of your leg having to go around your opponent’s head, you just need to get over one of their shoulders. Be careful and quick, it’s easy for your opponent to defend by moving his shoulder back in between your legs.
Starting from closed guard, your opponent has both hands on your collar, sitting in good posture with back straight. You are holding both sleeves around the elbows.
Next, you want to attack opponent’s right arm. Open your legs, sliding your hips to the left, push opponent’s right elbow in with your left hand, and pull opponent’s left elbow out with your right hand. This breaks him from his posture and brings opponent down onto you.
Raise hips in the air and throw left leg over opponent’s right shoulder, then lock legs into place by crossing your ankles. Continue to break opponent’s posture down by maintaining control of their left elbow.
Grab opponent’s right wrist with both hands and lift hips for the arm lock by applying pressure to the elbow joint.