I have a 6 week old kitten that isn't potty trained, she's peeing on the bed. I have a full grown cat who I was hoping would show the kitten how to use the litter box, but the older cat doesn't want anything to do with the kitten right now.

Can she get off the bed by herself? Maybe she wants to use the litterbox but can't get to it.
Some kittens are too small to climb into a large litterbox.
Otherwise, monitor her fluid intake and set her in the litterbox about 8-10 minutes after drinking.

I would sudjest just bieng persistant and keep placing the kitten into the litter box till she grows acustom to going into it she will soon enuf learn what its for and even when your full grown cat goes int oit as wierd as it seems place the kittem by it for her to whitness its use for her to see this also will give her the idea thet thats the place for going..

I adopted a kitten that spent the first few weeks of its life on concrete without a litter box. So we got a large kennel, like for a big dog. We put a very shallow litter box in there so she could get in and out, and she stayed in there unless we took her outside to play. They say it takes 3 weeks to break a habit, and we left her in there a good while after that. We put in a bed at first, but she got confused about the bed and pottied in there, so we took it out. She stayed in the kennel several more weeks than she probably needed to, but she got the message and did not have any problems after that, unless she had a bladder infection.

Well, I hate to seem rude, but cats climb trees and can't get down... so maybe she can climb on the bed but not off... fill the litterbox with dirt and little by little add kitty litter to it until she uses the litter. This may take up to a month to gradually change the litterbox from dirt to kittylitter.