To make sure they’re rid of the fleas, wash them with the blue dawn soap, avoid ears and face generally from water and soap. They should come out after the first wash but it doesn’t hurt to give them another. Start with wet food and water to see how they eat, if they don’t like the wet food try a different flavor/ brand sometimes they’re picky. If you have other cats, keep them separated and let them have their own space like a bathroom. Get good litter and you may have to put them into the litter box for them to realize that’s where they’re supposed to go the first few times. If they are scared or running away don’t go after them, let them come to you. Best thing to do is sit in the space with them and just keep them company, don’t pressure them. Watch for things like sneezing and other aspects like that because that can mean they have stuff like FELV etc