go to any pet store and buy some flee shampoo put the cat in the bath wash it down and apply the shampoo then wait how ever minutes the bottle says to wait then wash off and dry it works well or you can look up or call pet stores that do it for you that's what my Lil sister did
I'm not sure what the medicine is called but it's the ointment you put on their neck because that's the only spot they can't lick. I think you need a prescription from the vet but I'm not entirely sure.
The best way to get rid of fleas would be to give the animals a bath is flea soap and to also bomb the house. You can buy a flea bomb at the store and you are able to bomb the house and they will get rid of the fleas.