In this case, just put shredded paper in the box, then add a little bit of your chosen litter to the bottom....SLOWLY....a little bit at a time. Make sure it is unscented and non-clumping (until he gets older.) Good luck, it is a shame he was not taught at a younger age, but cats are clean and he should learn quickly. Oh, and try to keep him in the small area until he knows where to go.