>>263081AB has an application process, but they haven't opened it in a while. Which is odd because over the last year membership has declined steadily. The application is just a series of like 10 questions where they quiz you on torrenting best practices and also ask you what your favorite anime are and to explain why you like them. They don't actually care what anime you like, they just want the impression that you really like anime and manga and thus will have the incentive to participate in the tracker and community rather than just sitting on an account you never do anything with because the only anime you watch is Naruto on Crunchyroll.
Other than that, the only way to get in is to have somebody give you an invite, but for that to work the member who invites you has to be able to personally vouch for you and is held responsible for your conduct. That's why they don't let people give away invites to random people on the internet.