All you need to do is get under the car and with a long screwdriver lever the bendix gear on the starter out to engage the flexplate gear. Look at the mesh of the gears and it should be obvous how the starter needs to be shimmed to get proper alignment. Baiscally you want about .030 clearange on the gear teeth. It's pretty obvious when you get under there and check it.
You can buy shims at almost any large parts store.