I'm running MarketPress and ProSites on WordPress

I'm running MarketPress and ProSites on WordPress MultiSite. I'm trying to figure out how to create a registration form for people to sign up for their own shop. Right now I only have a free monthly option with a percentage transaction fees, though I might change my mind later. I'm not sure if that is relevant at all to getting this up and running.

I watched this video, and it mentions a plugin needed for users to choose their password and shop URL, but it doesn't reference the name of the plugin.

https://www.youtube.com/watch?v=16PT2GiUwVg&list=PLV1BcivFAIdsTVeVSROVN2SaBrBW3RKez&index=2