Select Share Screen in the bottom right and select the specific display, application, or tab you want to share. Click the Stop Screen Sharing button to stop sharing your screen (Figure 1 and Figure 2):
Figure 1 Share your screen
Figure 2 Stop sharing your screen
On the desktop application (only), a red border will show around the screen you are sharing and a floating screen-sharing indicator from which you can end the screen share (Figure 3):
Figure 3 Screen sharing indicator on SDA