If a challenge allows team submissions, you'll see a Team tab after joining. From there you can create a team and invite others by username or email, or request to join an existing team that's recruiting. Team invitations show up as notifications for the invitee to accept.
A submission made by a team is shared — every team member sees the same submission and any team member with edit permission can update it. If the team wins, prize payouts (when applicable) are split according to whatever the team agreed on and the creator's payout settings for that challenge.
