1. Click the Windows icon > Settings icon and select System.
2. Click Power & Sleep > Additional power settings > Choose what closing when the lid does.
3. Set "When I close the lid" to "Do nothing" and click "Save Changes".
4. Press the F3 key in hotkey mode and set the projection method to "Second screen only". At this point, you can operate the computer through the external monitor, external mouse, external keyboard and other devices when the computer is closed.