@deepdivetc, by "private" they mean that You can "get in" until You register, You cant see what is all about that site until You log in with the user name and password.
As for Your progress among trackers... all You have to do is... lets say... get into WCD (what.cd), make a Your way to PU (Power User) there, is not that hard (+ You have a seedbox), and there You will find Invite Forum to all major trackers out there.
Every major tracker have Invite Forum to varios tracker, the better tracker the better Invite Forum.
So... try to find someone (buy/trade, make a friend, whatever) who will invite You to WCD.
I hope that I help a little bit...
Regards