First of all, STAY CALM!! Are the kitten's eyes open? If so, then it is at least 3 weeks old. Go to the pet store and buy a can of KMR kitten formula (get the stuff already mixed as it's less of a hassle) and a kitten bottle (they should be near the KMR). Fill the bottle up with formula and warm it in hot water in the sink. Puncture a hole in the nipple of the bottle with a sewing needle. Do it a couple of times then squeeze it to make sure formula comes out. Hold the kitten in a towel in an upright position (the same position as it would be in as if nursing from it's mama) and put the nipple in it's mouth. If the kitten is as young as I think, you're probably going to have to feed it every 2-2 1/2 hours. When you finish feeding it, take a soft towel/cloth and rub it's bum (just below it's tail) until it pees and poops. You'll know because the towel/facecloth will get wet. You MUST do that in order to make the kitten pee and poop.

If you have a veterinarian, call them in the morning and see if they can take it and have the staff feed it until it's old enough to eat on it's own.

I admire you for taking this precious thing in. Please keep me posted.