Singer Quantumlock 14T957DC Detailed Threading Manual page 20

Threading Blue Overedge Stitch Needle:
Top Cover Thread Guide
Thread the top cover thread guide by slipping the thread under the guide from
right to left, and then pull the thread under the small round disk from the right
side.
Lay thread through Blue tension disk, while holding the thread securely with both
hands. Next slip into guide directly below the tension from right to left.