Backup Instructors are able, if needed, to take over a class by becoming the instructor. A Backup Instructor can also edit enrollments and other class settings.
During class, backup instructors go to the breakout control room during breakouts, but do not have a star next to their name in the classroom. Backup Instructors and TAs have the lowest priority for being shown on the participant bar and stage. They generally do not appear unless there are so few participants in class that there would otherwise be blank spaces on the participant bar.
Adding a Backup Instructor
On the class page, go to the People tab, and add Backup Instructors by typing their name or email into the "Backup Instructors" box.
Becoming the Instructor
If you are a Backup Instructor and need to take over the class, go to the gear menu and select "Become Instructor". This causes the current Instructor to become a Backup Instructor, and the classroom reloads for everyone. You will now be the Instructor of the class, and thus will appear on the participant bar and stage as the Instructor.