There is a Black Bar to the bottom of the video-screen. Pass your mouse or cursor on the Black Bar. When your mouse or cursor is on the Black Bar, you'll find, from the Left:
1) The Start/Stop Button
Click on this and the video/music will start to play. Click on it again and it will stop
2) The Speaker Button
Pass your mouse or cursor over the Speaker Button and it will show either MUTE or UNMUTE. To get the video/music to play click on UNMUTE.
3) The Volume Bar
When you pass your mouse or cursor over the Speaker Button, the Volume Bar is extended. You can then adjust the volume to your listening pleasure.
Important Note: If the video is not playing and you are not hearing the music, please click on UNMUTE on the black bar at the bottom of the video-screen.