how do I turn off my new iPhone 12?

You have a few methods to use in order to turn off your iPhone 12:

Method #1: Using the iPhone's buttons

There are two ways using the buttons:

1. Press and hold either the Volume Up or the Volume Down button and the Side button simultaneously until you see the slide to power-off slider. Drag the slider to the right to power off the phone.
2. Press the Volume Up button followed by the Volume Down button, and then, press and hold the Side button to access the slider. Drag the slider to the right to power off the phone.

Method #2: Without using the iPhone buttons

Go to Settings > General > Shut Down and then drag the slider to the right to turn off your phone.

Hold the volume up button and the side button until you see the slide to turn off option.

Go to settings, general, tap shut down.