The 2GT 16T pulley's teeth are not visible on the images.

Position the 2GT 16T pulley so that approximately 3.5 to 4 mm of the motor shaft protrudes. Ensure the pulley is not touching the motor.

Align one of the set screws on the flat side of the motor shaft and then tighten both set screws alternately until they are snug.

Attach the x-axis motor with three M3x18 screws. Don't tighten them fully yet. Note the orientation of the wires.

Finish to tighten the M3x18 screws while applying gentle pressure in the direction shown

Double check the pulley position and ensure it does not touch the motor.