Start by removing the 4 hex screws which loosens the base, then the top of the ball threads off to access the lens. You will see a set screw on the lens holder which holds the lens in place; you must loosen that to allow threading out the stock lens counterclockwise. Then in threads the new lens turning it clockwise setting focus while threading it in facing out as far away as you can while looking at a live video feed on a monitor. Tighten down the set screw when in focus & thread back in the hex screws at the base.