I use Feline Pine (pine pellets). You only need to line the box with an inch of it. It absorbs the urine and odor. Once it turns to complete sawdust, you dump the whole box. You'll need to remove the solid waste everyday.

Since the kitten is young, try putting him in a small room with just his box, food and water for 24-48 hours. He'll get the idea. That's what I had to do for Mollie Rose (9 years ago) and it worked!!

Good luck!!