The method shown comes from Microsoft directly on how to upgrade your system to Windows 10 Home or Pro depending on your current version of Windows 7 or Windows 8.
Media Creation Tool: www.microsoft.com/en-us/software-download/windows10
Q: Which version should I install?
A: (Go Under "Run Tool"): windows.microsoft.com/en-us/windows-10/media-creation-tool-install
Q: What if I want to downgrade back to Windows 7/8.1?
This video explores the ways of not only upgrading the computer in which this download is performed but also how to create an ISO image or USB device capable of booting Windows 10 onto a different computer.
Windows 10 FAQ's: www.microsoft.com/en-us/windows/windows-10-faq
Demonstration of upgrading to Windows 10: www.youtube.com/watch
This is How to Install and Upgrade to Windows 10 on Your PC. If you wish to keep all your files then click upgrade and not clean installation and key will auto activate. If it doesn't activate online automatically from the integrated BIOS product key, then you must wait for Microsoft to send a new key to your email confirmation you registered or reserved a copy with. You can still use Windows 10 in the mean time. Also remember that if you do a clean installation, you may have to reinstall some drivers (audio, etc) on the computer's manufacturer's website. Make sure you click WINDOWS 10 on the manufactures website when it asks you for which windows edition to install the drivers for. You can also restore back to your previous windows by searching "reset this pc" and clicking "reset this pc" in the search." Then click on "Restore to a previous windows version."
Make sure you have a genuine purchase of windows.
(You may buy from Microsoft store if you do not have)
Make sure you have a USB stick to download Windows 10 files to.