Lie on your back with your arms by your side.
You may wish to start with your affected arm lying on a pillow.
Squeeze your arm gently into your side, and then continue with moving your arm directly forwards and up towards the ceiling.
Imagine you are drawing a "J" with your upper arm.
Ensure you lead the movement with your thumb in front.
Control the movement as you reverse the movement, lowering your arm back down to the starting position.