Note: Before adding users to a group, you must first add those users.
From the AppGallery home page:
1. Click Users on the menu bar.
2. Click the Groups tab to see group information.
3. Click on the Group Name to see users in the group.
4. Click the Add a User button.
5. The Add Existing Users box will appear.
6. Click in the Select a User field and select the user(s) to be added.
7. Click Add when done adding users.