Premium Plugins & Premium Plugins Manager Plugin Integration with custom plugins in ProSites.

HI all,
I have some custom plugins developed to add special functionality to my online business using WP MU and Pro Sites. They appear in the Sub Site Admin left menu.
Firstly, how do I enable these plugins to be select-able as an option for Pro Site levels?

Secondly, which of the two plugins can do this for me (I'm not clear on the difference between the two: Premium Plugins & Premium Plugins Manager).