We are using Zoom for all our meetings. If you have not used it before, it's very straightforward.
The Oxford Branch has published extensive guidance and video tutorials on the use of Zoom.
Loss of sound during screenshare
Sometimes when a screen is shared, you can lose audio.
This is probably because you don't have sufficient broadband capacity to handle three video streams, the shared screen, the video from the meeting of all participants and of course the video you are sending.
In this case, you should turn off your video and on the screen with all of the participants click on the smallest of the three bars to remove the video download. You'll then just have a bar telling you who is talking.