Dell Precision Windows 10 Intel and Nvidia Graphics card.

I have a user who is experiencing issues with his display while using CAD. He has a Dell Precision M6800 i7 with 16GB of RAM and an internal Intel video card and also an NVidia. It sits on a Dell Docking station. How does the graphics management work for this laptop, I suspect the system is not using the NVidia graphics card as it should because when I disabled the Intel the screen completely blacked out. Is there a way to take the internal Intel video card out of the picture and only use the NVidia or set the Nvidia as the primary and the Intel as the secondary?