I'm setting up a sub site. I'd like to know what I need to know about integrating Membership plugin with it. People will be signing up for Membership at our main site. But when I log into the Dashboard for the sub site, I see a prompt to install Membership on it. Will I be able to make it so that people who are members on the main site are automatically members of the sub site, and if so, how do I make sure of this?