Activation of downloadable Windows 8.1

Need help. I set up Parallel 10. Used Windows 10 Preview as the OS. It's just a preview and doesn't access my files, etc. So I purchased Windows 8.1 full version from the Microsoft site. How do I go about setting up Windows 8.1 now as a virtual machine? Can't drag and drop the .exe file to where it requests a DVD, USB, or file. How do I set this up? Need to do it tonight to view a CAD/CAM program on a Windows format. Thanks in advance, Dr. Child.