Step 1:
Touch the App Drawer icon.
Step 2:
Touch Settings from App Drawer Menu.
Step 3:
In Settings, select “Display” located under DEVICE sub-menu.
Step 4:
In Display, touch Brightness option.
Step 5:
In Brightness pop up use the bar to adjust the brightness of your screen and touch OK. Optionally, you may turn on Automatic Brightness for automatic adjustment.