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.
Just wanted to note: If the mum isn't around, you can stimulate bowel movements and urination. Take washcloth and warm it with some tap water (not hot, just warm). Put it around your finger and stimulate the anus/vulva to simulate a mothers licking. This generally works with most of the orphan kitties we get at the clinic.
Although you did say she was defecating and urinating elsewhere, I too am curious about the real age. There's no use trying to get her to use a litter pan if she really is that young. Keeping up with lots of fresh towels/newspaper in her area may be all you can do until she is a little older.