Set the pulley to roughly elbow height and stand side-on with your working arm nearest the machine, elbow tucked against your ribs and bent to 90 degrees, forearm out to the side holding the handle. Keeping your elbow glued to your ribs, rotate your forearm inward across your stomach. Your torso should stay square to the front throughout; if you find yourself twisting to help finish the rotation, the weight is heavier than this small muscle group needs. Control the return back out to the start rather than letting the cable pull your arm back for you.