How do you get the keyboard backlight to function on a laptop? There are a few ways and I shall cover them with you.
From the BIOS
Dell: When the laptop is power up, press F2 until the BIOS appears then choose between 0% and 100%.
From the Keyboard
Dell: Press and hold the Fn (for Function) key then press the RIGHT arrow key.
From the Software
Dell: In Windows go to the Control Panel and search from the keyboard. The app will adjust the settings.