Press the Power button on the top-left edge of the Nintendo Switch console
If the console is in the dock, press the Power button on the console or the Power button on the controller
If the battery is empty, connect the console to power and wait a few minutes
If the screen stays black, hold the Power button for about 12 seconds, then press it again
If using a Nintendo Switch Lite, press the Power button on the top-left side of the console