In more recent versions of Microsoft 7 and Microsoft 10 you can use the search box in the bottom right hand corner of your screen to find display settings. Simply type ‘Display’ in the box and select one of the options that appear.
The below screenshot or similar will appear on your screen, allowing you to make monitor adjustments to brightness, contrast, screen resolution and text sizing. You might no see the ‘Change Brightness’ for the built-in display sidebar on Desktop PC’s that have an external monitor. To change the brightness on an external monitor, use the buttons on the monitor itself. These are usually under the bottom right hand edge of the screen. (See the manual for your screen type if you have problems).
The brightness slider appears in the ‘Action Center’ in Windows 10. To find the brightness slider in earlier versions, select Settings > System > Display, and then move the brightness slider to adjust the brightness.