When you look at the bobbin area, there's a metal half-circle. That's the driver. It pushes the hook around. When you put the hook in, it will complete the other half of the circle. It doesn't snap in, it just sits on the ledge. The ledge is called the race. When the hook is in properly, it will "kiss" the hook at the top. There should be a tiny space between them. Then put the race cover back on, with the "teeth" facing toward the machine. In Google Images, it looks like you have 2 tabs, one on each side of the race cover. They flip onto the race cover, onto a raised nub, and that will hold it in place.