Yes, you can add it to the empty NVMe slot and all you would have to do is set it up with Windows storage management. If it were me, I would use Macrum Reflect Free to clone the C: drive and expand the partition and use the 2Tb drive as my system drive. You can then use the orginal NVMe drive for storage after it is properly formatted. I would also look for a Gen4 X4 NVMe as they are faster and the PC supports the Gen 4 X4.
I am looking at a Western Digital BLACK SN750 NVMe Solid State Drive, 2TB.  It seems to be a gen3 drive. My desktop have 500GB SSD for C: drive and a 1TB drive for  Can I added the WD drive in an empty slot as the E drive?  Will this be a simple process?    
XPS 8950, adding WD 2TB SSD