It's very important that you take your new kitten to a vet as soon as possible. They can make sure (s)he is healthy and can help with options for feeding. When animals don't eat, they are usually either scared or sick. If it's the first one, then just do your best to keep things quiet, leave food out, and don't try to crowd the animal or force it to eat. They may only be comfortable feeding when there's no one else around and they have gotten used to their environment.
If they aren't eating due to illness, the vet will be able to diagnose the problem and offer a solution. They may also be able to board the pet, provide IV fluids, and high-nutrient food. They can help make sure your pet is getting the right kind and the right amount of food for its breed, size, and age. :)
Hope this helps! My wife works at a vet hospital. :)