Singer 14T968DC User Manual page 55

3. Thread the top cover thread guide by pulling the thread towards the left until
it slips under the guide. Then pull the thread along the right side of the
button as illustrated.
4. While holding the thread, firmly pull the thread between the tension disks.
5. Turn the handwheel toward you until the lower looper extends 5-10mm
(approximately ½") from the needle plate edge.
6. Thread the looper area of the machine following the green color coded
thread guides 4-9.
Three-Thread Overlock (narrow) page 8