To add users to your EDU account, go to the EDU admin panel ("+Import Users", invite by link/code or use any of the import options, here's how to import from Google Classroom).
If you've chosen the option to import by code or a link you might need to change the "Role" of the user.
To change the role from the default role (student) to teacher:
Go to "User list" (1).
(2.) Select the teacher(s), click "Edit Role..." in the purple menu that appears.
(3). In the pop-up dialog, change the role to "teacher" and click "Save changes"
(4). In the list of users, notice that the teacher's role has been changed.
(1) EDU admin panel - User List
(2) User list - Check boxes - Edit Role... (first make sure you have selected the user in the list)
(3) Assign role to user dialog (select "teacher" from the dropdown menu, click "Save changes")
(4) All users (the user's role has been changed to "teacher")
Now the teacher(s) account(s) is up and running, and the teacher(s) will have access to
1. The admin panel
2. Create groups
3. Administrate users (Invite students, assign/unassign students)
4. Create assignments