Once in the meeting, look for the Share Screen button at the bottom of the session window.

Clicking on the Share Screen icon will open the sharing options window. This window will show you a variety of options to share with the participants of your meeting, from the entire screen, to only specific windows or applications, to an interactive whiteboard.

To share your entire computer screen and anything you want to display on it, select the first option, here called Desktop 1. The first option on this screen will always be a full-screen share.  After it is selected, click Share in the lower right corner of the window to start sharing.

Now you are sharing your entire screen. The Zoom session window will disappear, but the application options bar will still appear at the top of your screen. The meeting ID will appear in a green box, next to a red Stop Share indicator.

To stop participants from seeing your screen without leaving the sharing screen, just click Pause Share. Anything you do on the screen while the share is being paused will not be visible to your participants. The green meeting ID box is replaced with an orange "paused" box. When ready to allow your participants to resume seeing your screen, click Resume Share.

To switch to a different sharing option, such as the whiteboard, you can click Stop Share and go back to the main session window and then click Share again to select a different option. To save a couple of steps, however, you can click New Share while sharing. This will take you immediately to the sharing options window to select a different item to share. Select a new sharing option using the steps for sharing outlined above.