I found an orphan newborn kitten in my porch ?

First get rid of the fleas by mixing dawn dish washing soap and water (half and half) and making sure it is warm and not hot. Soak a cloth in the solution and sponge bathe the kitten until her coat is wet and the fleas should die or leave her at the very least. Be sure to wrap her in a warm towel and keep her away from drafts until she is dried off. I assume when you got the formula you bought a bottle for feeding. Make sure the formula is warm also and not hot. She will have a hard time suckling at first. Remember kittens do not eat laying upside down. They are generally on their bellies and kneeding with their little paws. Try to imitate that environment as much as possible. Lay her on a towel on your lap and offer her the bottle from a position higher than her head to encourage her to suckle and kneed on the towel at the same time. The more you can imitate her mammas behavior the more she will thrive. This is the most important point and I hope the Vet told you. She must eat every two hours in order to survive. Even if she only gets a few drops. so if you cannot feed her make sure someone else does it for you and please don't get the formula too hot and do not serve cold. Don't be surprised if she doesn't survive in spite of all your good intentions. Sometimes momma cats will leave kittens behind that they instinctively know are not perfectly formed or are too weak to survive.