To join an Appbot team simply ask one of your colleagues who already has access to Appbot to invite you to the account. If that user doesn’t have the right permissions to add you they will be able to see who does, in their account. Only Team Leaders can add and remove users from an Appbot account.
It doesn’t matter if you already have an Appbot account or not. If you do have an account, the existing account will be added to the team when you accept the invitation. If you don’t have an account you’ll simply be prompted to create one when you receive the invite.