Since no one else seems willing to explain it, this thread is a tournament for invitees who have proven themselves to be good players of the BW, DPP, and ADV OU metagames. You can't just sign up, or even just sign up to be a substitute. They're hand-picked. (PS. I would delete your post if I were you...)
"All invited players are welcomed to confirm in this thread or privately via PM. All Player choices were decided by me with confirmation from the TD Staff, and we tried to do our best to maintain the highest competition possible. There were a couple players that did not receive invitations for one reason or another (mostly questions about their ability to play a tier or their activity). If you believe you were one of those players, feel free to PM me telling me why you should be able to join."