Creating a team
Once you have selected an avatar, the avatar will appear in the avatar pool for that team. This means that anybody in that team will be able to play using that avatar. However, there is a limit to the number of people who can play that avatar. This can be changed on the left. You can more avatars to any team by repeating these steps.
Global Mission Properties
The global mission properties box is the entire half of the menu next to the Team Properties box in the Game Settings Editor.