As a moderator, you can mute all participants. To do this, go to the three dots at the bottom right of your screen and click on "Mute all". This function is only possible if you participate in the video conference as a moderator on a computer. 

You can also do all but one , so that only that person can talk. To do this, go to the three dots at the bottom left in the tile of the participant you do not want to mute and click on the "Mute all others" button.

Or you can mute a specific participant only. To do this, go to the three dots at the bottom left in the tile of that participant and click on "Mute".

You can also mute yourself. To do this, press the microphone symbol at the bottom center of the screen.