Sit or stand up straight, facing a pulley.
Ensure the handles of the pulley are around head height.
Hold onto the handles with each hand, and pull down with your unaffected hand.
This will take your affected arm up, stretching your shoulder forwards.
Go as far as you can until you feel a stretch, making sure you are not leaning your body or hunching your shoulders.
Hold this position.
Control the movement as you bring your arm back down to the starting position.