You just bought it from Newegg.
They sent yo an email containing the license key, right?
So...
Go here:
https://www.microsoft.com/en-us/software-download/windows10
Scroll down and download this tool, either 32bit or 64bit, whichever OS you're doing this on
Run this tool
This will let you download the ISO file for Windows 10, or create a USB install drive.
Boot from that, and install on your new PC.
When you do the install, have ONLY the SSD connected. After it is all installed and working, then connect the HDD.