Navigate to your Content Page
Click on Roster
Scroll down to the bottom of the Roster and click Enroll People
Click the plus sign at the top of the page
You can now search by NetID or by name in the textbox
When you have found the person you want to enroll, click the plus next to their name
A drop-down menu will appear with the default option being student. Click on the menu and select Teaching Assistant
You can now click Save at the bottom of the page, and they will appear in your roster as a Teaching Assistant
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