Please see the article about managing users.
Only an Administrator can change the status of a user to be a teacher. To begin, go to the School administration menu (1) and select Users (2). You will see a list of all users in your school. You can sort the users by name, email address, or those who joined most recently (A). You can also search for a specific name or email address (B). After you have found the user, click on the settings icon (3)
Select the menu option (4) for the Teacher and select yes. Then click on "Save" (5).