If the teacher is already registered, follow these steps:

1. After signing into your admin account, click the "Teachers" button in your District Admin account.  If you're a School Admin, click the "School Admin" link in the left sidebar to find this button. 
2. Click the gear icon next to the teacher's name, 
3. Check the box next to "Register as school admin.” 
4. Click the "Save" button.

If the teacher has not been registered yet, follow the steps here first.