When you first open Microsoft Teams focus may be in the same region it was in when the app was last closed. The user interface, UI, consists in part of the App bar, which is on the left side of the screen in a narrow vertical column. The App bar has tabs for different apps, for example the Chat app and the Files app. Pressing ENTER on any of these App bar tabs opens that app in the rest of the window.
Please allow [01:06] to watch the following instructional demonstration on the Microsoft Teams user interface before continuing to the next topic.