You used to be able to get flea powder that youi sprinkled in the fur. Or get a flea collar, but that makes it's fur fall out around the collar area. Perhaps a bath.
Give it a wash in some warm soapy water and then dry off with a towel best you can then keep it in a warm place to keep warm and dry off. You should see many of the fleas coming off the kitten in the water or jumping off. It's better to do this than leave the fleas on as they can kill a young kitten. You can also use the proper stuff even on them when they are younger than the age on the bottle, that's a guideline thats only there to cover the company.
just asked a friend what they do in the RSPCA. She says that kittens of that age rarely have fleas. This is due to the fact that the mother cat would have been treated, which would give some protection to new born kittens. If they have to use frontline on young kittens, they use a small amount on cotton bud on the back of the neck
My wee kitten had fleas years ago and I just did the whole flea comb, catch the fleas and pop them between thumb nails thing. Made me itch like mad for hours though.