Kitty litter training please?

Well i have a 6Week old kitten that is an orphan because his mom got run over and killed when he was 3weeks old. I have been having to rub his bottom so he can pee and poop, but lately hes been doing that on his own all around the house. I have been trying to put him in the litter box but he just wont go there, he'll get right out. He just goes and finds a quiet place to pee and sometimes poop but he wont use the litter box. What can i do so he can use the litter instead of pooping or peeing everywhere? By the way i use any kind of litter, its actually called "Fresh Step- Clay Cat Litter-Non Clumping". Its no special kind of litter and i don't know if that's part of him not wanting to use it. :( Help!