I used kitty litter as substrate for a long time then i cleaned it out put aspen in his enclosure and a litter box full of cat litter. Now he poops in the litter box. When he craps some place other than his litter box I rub his nose in it.

(I was just kidding, I have not nor do I reccomend using cat litter for substrate. I do not nor should you rub your reptiles nose in his deficates.)