Place the end of the Bobbin in the Winder Centre A, forcing the Winder-Centre to the left far enough to allow the other end of the Bobbin to go into the Cup-end of spindle B. You will notice the Cup-end of Spindle is hollowed out, so that you may easily see the Pin that goes into the hole in the end of the Bobbin.
Be sure that the hole in the end of the Bobbin is right opposite the Pin in the Cup-end of the Spindle B. Then push the Bobbin Winder up aginst the the Balance Wheel, which will drive the Winder whilst winding.