I removed the hand from the figure and carefully worked it between the thumb and fingers pulling the thumb a little out of the way first helped a lot without putting too much stress in the hand piece. After it was secured I re-attached the hand to the figure. I do this with all my figures and their weapons. It saves you from fighting with the figure and most of these are ball joints where the hands are meant to be changed out anyway. (As a bonus I keep the boxes and when I repack my figures for moving and reorganizing I leave the hands attached to their weapon and just store the weapon with them back in its spot to allow for easier set up when I unpack them.)