Instead of installing and setting up a membership site on your main website here’s what I would recommend.

1. Setup ANOTHER install of WordPress on your hosting on yoursite.com/membersonly/ (the MembersOnly directory would be a new install of WordPress)
2. Install both a membership plugin (see below) and buddypress on this new site.
3. Use a buddypress theme (here’s some amazing ones!) this will save you the hassle of needing to setup your theme with buddypress templates.
4. Configure and add content then you’re all set!

Community Plugins:

Buddypress: http://buddypress.org/

Membership Plugins:

Wishlist: http://member.wishlistproducts.com ( $97 – what the pro’s use)

s2Membership Free: http://wordpress.org/extend/plugins/s2member/ (limited to PayPal integration)

s2Membership Paid: http://www.s2member.com/ (Lot More Options)

‘Jigowatt’ Premium Content: http://codecanyon.net/item/wordpress-premium-content/137192?WT