How many kittens do you have? The minimum number of litter boxes "needed" right now is equal to or greater than the number of kittens.
Basically just set up shallow trays of non-clumping litter like they have in the adoption windows of the pet store. Some people would say spread them out around the house and keep them very separated from the food supply, but I would keep them closer to the headquarters set up by the mamacat. Maybe put the pans in the same room or adjacent rooms?
Change them as normal. Look for mamacat to teach them, but if they seem confused you can gently place them in a litterbox so they get used to the feel. No big production -- just use it as a part of getting them used to handling and socialization with humans. A lot of using the litter box is instinct.
Besides that, just remember to have patience and not expect too much right away.