Make sure both monitors are connected to the NVIDIA-based graphics card,
- Open the NVIDIA Control Panel. You can do this from the pop-up menu when you right-click on the desktop.
- Under the Display category, select "Set up Multiple Displays"
- Check the box next to the inactive display you wish to activate as a secondary display and click apply.
- If your display is not shown, click "My display is not shown..." to force detection.
- You can drag the green boxes around to match the physical arrangement of your displays, and choose which one is primary by right-clicking on it and selecting "Make Primary".