Find out if your notebook has a backlit keyboard
From the Apple menu , choose System Preferences and then click on Keyboard. If the Keyboard preferences window has an "Adjust keyboard brightness in low light" checkbox, you have a backlit keyboard.
Adjust your keyboard brightness automatically or manually
You can have the keyboard brightness adjust automatically based on available light, or you can adjust it manually.
Adjust the brightness automatically
To set your keyboard brightness to adjust automatically:
- From the Apple menu, choose System Preferences, then click Keyboard.
- Select the "Adjust keyboard brightness in low light" checkbox.
Adjust the brightness manually
To make the keyboard brighter, press F6 on your notebook's built-in keyboard. To make it less bright, press F5.
If you can't adjust your keyboard's brightness manually, it's likely because you're in a very bright environment and you have your Mac set to automatically adjust the brightness. In this case, the backlit keyboard turns off. When you move to a location with less light, you can once again adjust the keyboard's brightness.
Adjust brightness on your MacBook Pro with Touch Bar
If your Mac has a Touch Bar, you can quickly adjust your keyboard brightness by tapping 
in the Control Strip:
The Control Strip expands, and you can tap 
to adjust keyboard brightness:
Learn more
If you use Boot Camp and your keyboard isn't working as expected in Windows, you might need to update your software in Windows.