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A user without a team can't do much. All the games belong to the teams, so unless a user is a member of a team, he neither would see any games, nor be able to join any.
Setting up a team
Go to the Team configuration (the link is located in the top menu)
Setting up a team is fairly simple — just click Create and start adding team members.
Inviting participants
Once you create a team, you'll be able to add new participants.
To invite a new team member — fill in his email in the form and submit.
He will receive an invitation email, which contains a link to join your team.
New user account will be automatically created.
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All free teams are limited to the 5 participants.
If you need to increase the limit — consider upgrading to another plan.