From the home screen, swipe down the Notification bar.
Tap the Settings icon.
Scroll to and tap Display.
Tap to check or uncheck Automatic brightness as preferred.
Tap and drag the slider to the preferred brightness level.
Once finished, tap OK.
Note: To quickly adjust the screen brightness, from the home screen, swipe down the Notifications Bar, then tap and drag the slider to the preferred brightness level.
Tap the Auto icon to set Automatic brightness.
To change the brightness between 0%, 50% and 90%, tap the brightness icon if preferred.
Tap Screen timeout.
Tap the preferred time setting.
The backlight settings are now changed.