OK, I don't have a diagram but here's how it's done. Put a spool of thread on the spool pin to the right rear of the pillar. Bring the thread forward to the bobbin winder tension on the bed in front of the pillar making sure it's between the tension disks. Then pull the thread up to the bobbin which is on the bobbin winder shaft. Stick the thread through the little hole, or wind it around the center of the bobbin, how ever you prefer, then lift the lever underneath the bobbin winder till it locks into place.
Turn the stop motion knob in the center of the hand wheel counter clockwise to release it, then using the foot controller start the machine. Run it till the bobbin is full. It should disengage when full.
That's about it.
Joe