Lara, this pic is from a Slant-O-Matic, but the principle is the same.
http://www.quiltingboard.com/vintage...ml#post5805276
your bobbin case will have a "Groove" that matches up to the "tongue" on the hook.
And you're not stupid! It's a non-intuitive design. Once you've done it once, it's a snap, but if you haven't done it before it's awful to learn without a guide.