A Teacher Group account has a single owner who sets up the account, chooses the group name, and provides payment information.
When the signup process is completed, the administrator will have access to a dashboard where they can invite group members via email, or with a special signup link. The group owner can also allow other group members to manage the group invitations and member list. Group members can be added and removed at any time. Teacher Groups automatically renew monthly or annually.
Managing Your Group
From the "My Account" page, find the "My teacher groups" link on the right hand side of the screen.

The administration area shows the list of people in your group (currently just yourself).
You can use the "Invite new member" button to invite new members, or the "Remove" buttons to remove anyone's access.
The invite area allows you to individually invite members, or give them a special URL that allows them to sign up.

If you enter a teacher's email into the "Email" field and click "Add Member", the teacher will be sent a personal signup email. Once they go through the registration process, they are automatically added to your group. You'll also see that you can preset the role of the member you are inviting.