Automatically add vendors when registered on Joomla?

Hi,

I have Jomsocial installed on my site, and I am using MembershipPro to register new users on my site, so that they can pay the appropriate subscription fee.

I have two user groups - one free, and one paid, set up through Joomla ACL. The paid group should have access to Hikamarket.

The problem is, when users register on Joomla, they're not automatically added to the Hikamarket vendor list. How do I set this up? A link to the Joomla ACL instructions would be good.

Thanks.