How do I set the timing on my Singer 750 sewing machine?

I took the bottom off & saw that the 2 gears under the bobbin was stripped. I am somewhat mechanically inclined & the man that usually works on my machine couldn't work me in for a few weeks. I bought the gears from him & he warned me that it would be a project if I didn't know what I was doing. I had no problem getting the gears on but now I need to reset the timing. How do I do this?