Welcome to the forums Paulleville! You can buy a centering jig from Woodcraft or Rockler. Just be sure to get the one for your type router. Or, if you have a set of bushings for your router you can simply remove the base plate, put the 1/4" ID bushing on the base plate and insert a 1/4" rod or bit in the router. Then all you have to do is slip the plate with the bushing on over the rod/bit and re-attach the base plate. The plate should then be centered on the router.
Fort Worth, Texas
City where the west begins.