To change the volume of a video you can either use the volume control on your device, or the volume control of the video player, located at the bottom right of the video.
To adjust volume through the video player, hover your mouse over the volume icon and a volume bar will appear. Click on the bar to select the level of volume you prefer.
To mute the video player, click the volume icon in the bottom right of the video player, which will stop all sounds.
To unmute the sound, click the volume icon one more time.