To register to join a team, all you need to do is post an approved copy of your character registration here. You can add what team you'd like to join if there are any available or you can even post who you were hoping to team up with.
Name: Doe, John
Age: 137
Appearance:Looks like a football
Personality:Acts like a weirdo
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Clan:none
Village:yukigakure
Element:earth
Rank:genin
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Biography:You don't want to know.
RP Sample:
THIS IS NOT WHAT YOUR CHARACTER APP SHOULD LOOK LIKE. THIS IS ONLY FOR AN EXAMPLE.
Your kage will look at your application and if he has any available spots on existing teams or a sensei waiting for genin to teach, he will assign you to a team. Keep in mind that the team isn't complete until there is four members. If your kage has the requirements needed to assign you to a team but has looked here in a day or two, feel free to ask a moderator for help.