Shut down your Mac

Press and hold the Command + S keys while pressing the power button to turn on your Mac.

It is best to start holding the keys before the screen turns on or you hear the startup chime. If you see the Apple logo, then you need to shut down and to do this step over. Except on a Mac with a T2 chip, the Apple logo will always appear the second the computer turns on.

You should see a black screen with white text.