The only HDMI port on your XPS 8950 will be in the area between #2 and #5. The onboard Intel Graphics port you have is DP, in area #1. So there's only one place to connect your monitor. If monitor didn't come with an HDMI cable, you'll have to buy one. [IMAGE] There shouldn't be any problems using HDMI at all. And look at it this way, video/audio over USB-C is up-and-coming tech. So this monitor will be "future proof", at least for a little while.  If you ever decide to add a second monitor, get one with a DP input and connect it to one of the three DP ports on the video card, rather than to the DP in area #1. You'll get better overall PC performance that way. BTW: If you have a laptop, without HDMI output, that supports video/audio over USB-C, you can use this monitor directly as an external display for that PC. Post back and let us know how you get on...
Upfront, please realize that my knowledge of ports and recent monitors is very lacking.  I have a problem similar to others.  I ordered a Dell XPS 8950 desktop which arrived a few weeks ago.  Upon ordering it, the order web page displayed other accessories at the bottom and so I ordered the S2723HC USB-C monitor, assuming that it was compatible with my desktop.  The monitor just arrived belatedly today.  I connected the accompanying USB-C cable into the monitor, and into what I >>thought<< was the USB-C port on the back of my 8950 desktop (my 8950 diagram has it labelled as a USB-C 3.2 Gen 2 x 2).  So when I turned on the PC and monitor for the first time, I got a message on the monitor that there is "no HDMI cable".  There was no HDMI cable provided in the shipment.  So the obvious first question - did I just buy a monitor from Dell that is incompatible with the XPS 8950 I just bought from Dell, and if so, do I need to return the monitor and somehow find a compatible one?  Thanks for any help. 
XPS 8950, no HDMI cable