How do I properly insert a needle into the Brother XH2135-001?

Insert the needle with the flat side toward the back of the machine until it touches the stopper. Then securely tighten the needle clamp screw with a screwdriver. Make sure to insert the needle until it touches the stopper and tighten firmly, otherwise the needle may break or the machine may be damaged. (Page 1 — XH2135-001)