How do I properly insert and secure the needle in the XG4099-001?

Insert the needle with the flat side toward the back of the machine until it touches the stopper, then tighten the needle clamp screw securely with a screwdriver. Make sure you insert the needle until it touches the stopper, and do not use excessive force when loosening or tightening the needle clamp screw. Before replacing the needle, place fabric or paper under the presser foot to prevent the needle from falling into the hole in the needle plate. (Page 1)