The power button can be found on the bottom in the middle of the monitor.
Open System and select Display.
Here you can change which is the main monitor and to extend to the external monitor and not duplicate.
Please see the guide here on how to install OnScreen program.
Open the Start Menu, search for OnScreen Control and open the app
Here you can choose how the external monitor displays multiple programs.
You can chose which programs are split and have programs full screen.
Below is an example showing the screen split in to two windows.
Below is an example showing the screen split in to six windows. When moving programs into the splits areas you will see lines to place them within splits.
From the Monitor Settings you can change the monitor brightness and contrast and orientation.