How do I turn off my newly installed Windows 10 computer?

Unplug it, throw it in the washer, then in the dryer, then back in the washer, run over it, go "office space" on it, burn it, then by a mac.

Or if you go to the bottom left of the screen there should be an option to shut it down. There's also a button like that to the right of the screen. Also on any Windows Computer look for a power button. Either on the front of the computer tower (desktop), or on the top of the keyboard (laptop).

Look on the start menu find power then select shutdown

Most people use either the power button, or select "Shut down".

The same way you turned it on.....