Hi,
when you are watching a non-VR video,
1.Play the video and click to call up the panel.
2.On the top of the panel there are four buttons, click “Cinema Scene” button( the first one from right )and you will see the option to change the cinema settings.
3.There are three options(Front, Middle, Back) under "Change Cinema Seat" at the bottom right corner.
Hope this helps :)