Ok. You can call a local vet and ask them for help, but here is my info (we just finished raising a litter).

You need to go get kitten formula, and a special bottle made for babie animals. Try to get formula with colostrum, just because s/he is so young. Run hot water into a big glass and set the bottle of formula in it. When it is kind of warm (test in on the inside of your wrist, NEVER FEED THEM SOMETHING THAT YOU HAVE NOT TESTED!), take it into her and put the nipple in it's mouth. If it seems that it is having trouble, gently squeeze the bottle (not too hard, you can possibly choak it).

You need to keep it warm, and in a cozy place (a good-sized box). I would reccommend putting in an old stuffed animal to act as a "mother figure". You should feed her every 4 hours. When you can, take her into a local shelter and have them look her over and give you some information. You could also go to the vet's, but then you'd probably have to pay a fee.

I hope I helped, just let me know if you need any more!