The Display Shortcut
Press Windows Key + P, there will be a pop up on the bottom right.
Select "Extend", to use both screens
Refresh the Connection
Unplug the HDMI or USB-C cable from the laptop.
Wait at least 5 seconds, and plug it back in firmly.
Graphics Driver Reset
If the screen is still black, press Windows + Ctrl + Shift + B.
You will hear a beep— this restarts the graphics driver and often forces the monitor to wake up.
Arrange Monitor Display
Go to Settings > System > Display
You will see two boxes labeled 1 and 2.
Click Identify it will show the label on both monitor
Click and drag the boxes to match where they sit on your desk. Click Apply