For the past couple of years, Acer has been releasing several computer monitors, each having their own sets of features, characteristics and price points to target different audiences. Despite their differences, Acer devised a common OSD (on-screen display) interface which lets you quickly control the screen brightness of your Acer monitor, as well as other options.
The hardware buttons can be located on the side or bottom of your Acer monitor, depending on the model. Pressing any of these buttons aside from the "Power" button will bring up the OSD. These on-screen buttons are aligned with the hardware buttons, so pressing the hardware button will open up the associated section. To adjust the brightness, you have to open the Menu section (depicted by a "Context Menu" icon. From there, the "Brightness" option appears and you can adjust the value using the left or right buttons.
In case you are unable, or do not wish, to use the OSD interface, you can adjust the screen brightness using a third-party software such as ScreenBright or Dimmer (links in Resources). These apps may also offer brightness adjustments beyond the hardware limitations of Acer monitors.