Hi Krista,
Were you able to get it figured out yet? There's no code to use, but sometimes xcart can be glitchy. I would try logging out, clearing cookies/cache, and then logging back in. That usually fixes any weird problems. Also, the kit should be added to your cart automatically, so you shouldn't have to add it in yourself.
If you've already checked out and were charged for the kit, I'd send an email to Robin at
admin@sweetshoppedesigns.com, and she can get you fixed up.