Why won't my cat clean himself after pooping or stop stepping in it?

This is hard to do. He probably never learned to clean himself or he is so disgusted by his own poop that he does not want to clean it up. 1) his box needs to be cleaned everyday 2) you can put some hairball remedy on his paws so he is enticed to clean that off, then put some on his fur further back until you can put it on his bum. He may get the idea. 3) wipe his bum and feet with clean wipes. He apparently also never learned to cover his poop. This unfortunately happens when the kittens are taken away from mommy way too early, as their mom actually teaches them all that.