Make sure you have a short-walled container for the litter box. We usually use one of those cardboard boxes that hold canned goods. Urine you can't do much about but with the feces, wherever the kittens would dedicate, we would pick it up and put it in the litter. They would eventually get the idea. Cats also have a natural instinct to cover traces of themselves so you can also get the kitten to want to be in the litter box and dig by helping the kitten do it. Have the kitten in the litter box and manipulate his legs to have him dig.
As others have mentioned, is he really two weeks old? If so, he isn't exactly ready to be using the litter box. He needs his mum to stimulate him to pass.
Opportunity is missed by most people because it is dressed in overalls and looks like work. ~Thomas Edison