Is it a 628? Or is it a 620? If it's actually a 620 (the numbers are hard to read) You might have already figured it out, but, if not, here you go: Slide the silver slide plate towards until you can see the bobbin....do not remove the bobbin....and make sure it's an empty bobbin. Now look for a little white/creme colored button to the left near the bobbin...push that button down. Now make sure your sewing machine is threaded exactly as if you were getting ready to sew (with needle threaded). Move the stitch lever down to 6 or 7 and make sure your machine is set for "Low" at the upper right ...slowly step on your foot peddle and the bobbin will rewind while still in the bobbin case. Take it slow until you feel comfortable rewinding the bobbin. When you're done just close the slide plate (don't touch that little button) and you'll here a "click" ... The slide plate has pushed the bobbin winder button down and you're ready to sew!