XPS 8920, adding a second HDD?

It is a hybrid hdd: a large hdd+very small NAND ssd. Install it like a regular 3.5 hdd.  Initialize it in Windows disk management.  You do not need the small 64 mb ssd part.  Just leave that part alone.

It's a 3.5" standard HDD and will work with your XPS 8920.  I think hybrid drive mentioned was a typo description as the WD10EZEX is just a standard "blue" drive made by WD, it is not an SSHD.

For proper installation with ease, prior to adding new HDD, go to BIOS settings to verify if AHCI is enable in SATA operation mode.  If current mode is set to RAID, you will need to make the change by following this tutorial.  Only after the system can boot in AHCI, you can then adding the new drive.

After new HDD installation, go to Disk Management and accepting popup to initialize with GPT.  Right click on new disk (the one with unallocated space) and select New simple volume.  Follow the wizard to complete setup the second HDD (mostly accepting defaults).  When the wizard is complete, your new drive should be ready to use.

Thank you both for the help.

One more question. My 8920 came with a license for Win 7 Pro. I have since upgraded to the anytime upgrade to Win 10 Pro. Do I need to install Win 7 first and then do the upgrade or can I just install Win 10 and use the Win 7 license that I got from Dell.

There is no need to reinstall Win 7.  When you did the upgrade to Win 10, a digital license has been issued to your machine hardware IDs and MS kept a record of it.  At anytime you reinstall Win 10, it will be activated automatically when system get connected to internet.