Congratulations, but my what a surprise. I can relate. It's happened to me before too. Rabbits are notoriously difficult to sex correctly at the time of weaning/purchase.
You might find the several care articles at House Rabbit Society,
http://www.rabbit.org , useful to you in this endeavor.
Keep an eye on the kits, checking and handling them daily so that they will be used to being handled. The mother should be keeping them clean, but if she is not doing so because she is so young and it is her first litter, you will need to do this. Wiping their bottoms off after they have been fed.
I am guessing that your doe is quite young. My experience with does that were accidentally young mothers has been mixed. First time mothers can be more nervous and difficult than more experienced mothers, sometimes even stomping or cannibalizing their young. If for any reason, something should happen to your doe or to her ability to properly care for her young, you may need to feed the babies yourself with an oral syringe. There are many good recipes for formula. Here's one from "Care of the Domestic Rabbit," by Dr. Chris Hayhow, current president of ARBA:
500 ml whole milk
30 ml light corn syrup (Karo)
2 Tablespoons powdered mild
1 1/2 teaspoons bone meal
2 egg yolks.
Rabbits can apparently also nurse on goats milk and some kitten formulas. . .
Keep us posted on how you are doing. Without asking, you have gotten yourself into a potentially wonderfully rewarding experience. What breed is she and how many kits did she have? Take pictures and videos and keep records of how the litter progresses. To keep the different kits recognizable, you may want to mark the inner side of the outer ear with a sharpie, using a numbering system. You will probably have to refresh the markings every couple of days. . .