Multiple Stores in Marketpress?

Using Marketpress I can make what seems to be one store.

For lack of a better term, I've got a "directory" set up with 4 businesses - is there a way to give them EACH their own store? I thought Category < Parent Category, but that didn't work...

I need (essentially):
http://www.domain.com/store/StoreOne/foobar/
as WELL as
http://www.domain.com/store/StoreTwo/christmas-pudding/

like two root stores instead of clumping them all into one store.. how would I go about doing this