Pop out the case by its little handle. Insert the bobbin so that the loose end points in the same direction as the slit (off to the right). Pull the loose end through the slit and into the little notch. Now put the case and bobbin back in the machine, pulling out the handle on the case as you do, and then pushing it in. Then close up the outer case and turn the wheel toward you so the (threaded) needle goes down and picks up the loose end of the bobbin and pulls it through the plate.