Singer 6268, needle timing advice

Question

I have a Singer Sewing machine, Model #6268. The threads have knotted up on the underside of the material. When I finally was able to pull it all out, it caused the needle to hit on the bobbin plate (hope that is right). Now the needle is bending, not going through. How can I adjust it back as it supposed to be? I have had this happen before, but it cost way too much to get it repaired. And I still don't know why this happens (the threads getting tangled).Thanks!Cheri [e-mail]