How do I act as a user in the Teacher app on my iOS device as an admin?
If you are an admin, you can act as instructors in the Teacher app and take any action in the app as if they were the instructor. Only account-level users with the Act as users account permission can act as other users. This permission does not apply to sub-account admins.
Act as User

Tap the Act as User link.
Note: If the Act as User link is not available in your user menu, you do not have the permission to perform this action.
Enter User ID

In the User ID field [1], enter the Canvas ID number for the user. The domain will already be populated for you [2]. Then tap the Act as User button [3].
Note: The user's Canvas ID can be found as part of the user's URL in the web version of Canvas. Make sure you have the user's ID associated with the correct Canvas URL.