New cage and potty training

My roommate and I recently switched to a new cage (Feisty Ferret) and our previous cage had a solid bottom which we covered with bedding. The new cage has wire bottoms which we have covered with fleece that is chinchilla-safe and put in a corner litter box with bedding, but they are only about 5 months old and still pee in other places. Is there anyway to get some sort of addition to the cage which would allow us to cover with bedding? It doesn't smell as good as it did with all bedding, and I feel a little bit out of my element here. Any advice would be greatly appreciated!

Also - if there is a forum that would fit this type of information, I would love to know what it was, because I had a hard time finding information on this type of thing!