This is an all grain kit, right? If you have spare grains you can do what Gila said above.
If you don't, you can mash the grain from the kit, and after you get all of your runnings for the brew, sparge a little extra, boil it for 20 minutes, cool it, and dump in the yeast. Unfortunately, it will take a few hours for the yeast to ramp up, so you'll have to let your wort sit for a few hours before you can pitch. However, if you keep the wort sealed during this time it should be just fine.