Kittens learn this very quickly. You'll need a litter box with short enough sides that they'll be able to get into and out of. Just place the kitten in the litter box and gently use your hands to move the kitten's front paws in the litter. They'll get the idea what to do. Have the litter box located in a place (NOT near their food and water) where they can access it readily. Either have more than one litter box or clean it out several times a day.
You can litter train your kitten by getting a litter scooper and then putting it in an appropriate location for the kitten. Take the kitten to the litter pan and put it in there so that it can help itself every so often. Make sure that the kitten tries to dig into the litter and if it doesn't, show it. This will help the kitten to understand what the litter is for. Read more on http://www.wikihow.com/Litter-Train-a-Kitten.