I have just got a 6 week old pup an d noticed a flea what is the best thing to do... I have no other pets

You can get flea and worming treatment from your vet. The pup should have a thorough check over by the vet anyway as (and I'm just assuming) you bought from a less than reputable breeder.

You want to get rid of the fleas asap because they can (and will) transfer to your furniture and maybe even you. The best thing to do is to give them a flea bath with flea shampoo (not too expensive) or take them to a groomer who will give your dog a flea bath (some will) and then you can get a flea treatment appropriate for your dog to prevent further need for treatment and also you may want to spray your house with a flea spray to get rid of any little guys who may have jumped ship. Hope that helps.