Marketpress Multiseller tutorial?

Hi there!

I've just bought Marketpress just for his amazing feature to let user create own shop and add their own products.
Just one problem....i tried and i tried again but nothing registred user cannot add product.

I've set up a multisite.
I've installed buddypress
I've tried to install capabilites and role manager plugins trying to solving this by assign role "add_products" to new "seller" role..but these rules (add_products, edit_products..) don't appear on rules list.

Now...what i have to do? is there any tutorial about it?
I'm stuck on this problem and i can't finish my work!

And thanks for your daily great job!