MarketPress and user access / registration

Hi wpmudev.

I have signed up for an elite account and installed MarketPress and frameMarket theme.
I want to make a website where theird party can sell their products.
When I add new user they can't add any products. The user role is author.

Do you have a plugin that is perfekt for users to registre as merchants on my site?

That's it for now.

Best regards.

Tim Bøttiger