Adjust brightness in Windows 8

METHOD 1

• Drag the cursor towards the top right corner of the screen. This action will expose the 'Side Charm Bar'
• Click on the 'Settings' gear icon
• Click on the 'Brightness' icon which will reveal a vertical level meter. 
• Drag the level tab either to the top (increase brightness) or to the bottom (decrease brightness)

METHOD 2

• Right-click on the 'battery' icon at the bottom right part of your screen.
• Select the 'Adjust Brightness' option which will reveal a window containing a 'Screen brightness' level meter 
• Drag the level tab either to the right (increase brightness) or to the left (decrease brightness)