If it keeps using the carpet, the best thing would be to confine the kitten in a small room or a cage with the litter box. My kittens were born feral (meaning out in the wild) and had accidents for the first few days but then starting using the litter box. It's natural for them to want to cover their waste to hide from predators so that's why they take to litter. It could also be the litter you are using, some don't like litter that smells too much, try using clumping kind, and also make sure the litter box isn't too big that the kitten has trouble getting into it. Rubbing noses in it doesn't work for cats but you could place her in the box after she wakes up or after she eats or plays hard. Hopefully the kitten will get the idea.