How do I switch sound back & forth from TV and computer.

Right-Click on the sound button in the bottom right of your screen and then click:”Playback devices”.

To hear sound from your TV click on the HDMI and then press "Set as default" at the bottom and then when you want to hear from your computer speakers click on “Speakers” and then press "Set as default" at the bottom.

If you are connected to the TV and you do not see the selection "HDMI" then right click and check "Show disabled devices".