When the laptop or computer is connected via HDMI cable to the wall HDMI port or TV...

Press and hold the “windows” key (found between the left 'ctrl' or 'fn' and 'alt' keys)

Tap the “P” key then you can release all keys…

A display will appear like this one below…

Select the “duplicate” selection and this will make the screen on the laptop/computer stay on and what is shown on the computer screen will match what is on the TV