Performing rotation exercises will help restore mobility and build strength. Small arm circles and shoulder rolls are examples of rotation exercises. For further details about these exercises please see the link below.
Performing strengthening exercises lying on the floor puts less stress on the shoulder and can help reduce the pain. Lie on your good side, and raise the affected arm towards the ceiling. Slowly rotate the arm in one direction, and then rotate is back in the other direction. Gently work up to standing exercises.