You don't sign up as a team, you sign up as individual players, and there will be a thread made at the beginning of the season for player signups and I think at midseason as well?
I think in dungeons where links will be used they made it so that normal chat worked like a link chat? Been a while since I tried it, does anybody who did this last christmas event remember?
Seriously, this may be the best part of the entire series in the Manga. Latest chapter was fantastic. Somebody needs to let me know when the anime reaches this point someday.