Once you've connected your laptop and want to make optimal use of the monitor, double-check that all your Windows settings are correctly configured.
Select Start > Settings > System > Display. Your PC should automatically recognize the monitor and display the desktop. If the monitor isn't recognized, press the Detect button.
P.S. If this doesn't work, please check your cables and laptop's compatibility. (FAQ - How do I connect my Windows laptop to a desk?)
In the Multiple displays section, select an option from the list to determine how the desktop is displayed on your screens. Then, don't forget to click Keep changes.
When using multiple displays, you can choose between different display modes. You'll find these options under Multiple displays. The Duplicate these displays option makes the content on all screens identical. To correctly expand your workspace, choose Extend these displays. This allows you to spread windows across the different screens.