Take your kitten to its litter box right you bring it home. Sometimes that first visit is all is necessary. But until you're sure that the kitten understands, take it there after every feeding. Sometimes felines won't use a litter box if something about the particular make of litter is never to their liking. Once in a while they will stay away from the container if its location is not private enough. Try to solve these problems if the kitten will not use the litter box right away.
If the vet gives you medicine for the kitten, make sure that you or one of your parents knows how to give medication. Ask the vet or the vet's assistant to show the proper method. Give the medication to the kitten exactly as aimed by the vet. Twice per day is not good enough if the kitten is meant to get medicine three times each day. Young kittens like to eat every few hours, about four times a day. At each meal, provide a saucer of fresh milk alongside a small dish of dry cat food. For one or two of the meals, blend in canned food (meats or seafood). If the kitten gets diarrhea, change to powdered milk. If the diarrhea continues, reduce the amount of dairy and the amount of meals at which it is served.