@odu.eduif you are an ODU student.
You can control which person occupies the large central area of the call window on your own screen. Simply click on one of the thumbnail images at the bottom of the call to bring up that person.
Once the call is underway, move your mouse to the top and left edges to see the (normally hidden) control icons available to you.
Near the top you should see these controls to, from left to right, add more people to the call, mute or activate your microphone, turn your camera on and off, adjust bandwidth use, alter your settings (may be useful in selecting which microphone or audio device to use), and to leave the call.
Moving your mouse to the left should reveal a vertical list of plugins.
Of particular note is the which is for screen sharing.