After you sign in, Cisco Jabber Video displays its control window.
If you want to open your video window before a call to check your camera angle or your hair, click the Show video [icon] button on the upper-right corner of your Jabber Video control window.
During a call, click the Show video [icon] button to bring your video window to the front.
(Mac only) You can also open the video window from the main menu by clicking View > Show video, or with the keyboard shortcut Command-2.