How to shutdown an IPhone X

To turn it off, hold down the side button and one of the volume buttons simultaneously until a slider appears to turn off your iPhone X (There will also be the slider for the medical chart, as well as the slider for an emergency call)

Then drag the appropriate slider to turn off the iPhone X.

You can also turn off your iPhone X by navigating to

Go to Settings and then to the General section

Tap Shut Down at the bottom of the Reset tab.

To turn it back on, press and hold the side button for a few seconds