I have installed the Membership Premium Plugin on my WP MU

I have installed the Membership Premium Plugin on my WP MU site teamsheet.me and I get prompted with this message: "The Membership plugin is not enabled. To ensure your content is protected you should enable it" When i follow the link I get this message "You do not have sufficient permissions to access this page." I am a valid WP MU member and I don't see what extra permissions I should need?