Live Rooms has a few different options for viewing. The first is the toggle button between Live Streaming and Conferencing. The third is a screenshare from a local computer. This documentation shows how to change between the these views.
Live Stream and Conference Toggle
This first screen shot shows a live room with two people. It's currently showing a live stream. Click the Toggle button to go to conference view.
Once you're in conference view (image below) you can always click the toggle button again to return to the live stream.
Screen Sharing begins with the screen share button. You'll find it at the center of the bottom panel. Click this button, and you'll get a pop up to share an entire screen or a single window.
Once you've selected a screen to Share everyone will be able to see the screen. The resulting conference will look similar to a live stream.