if you still have the mother cat, bring the kitten to the litter box and the mother should show the kitten what to do. Also, try bringing the cat to the litter box a lot until it learns.
If a kitten is using another area pick up the deposits and place in the litter tray pop the kitten in and gently scrape their front paws in the litter.
I have had cats my whole life and what you do is take the kitten and put them in the litter box and take their front paws and dig them in the litter do this a few times and they should catch on pretty quickly.
