BTW you can find working keys for W10 Home for as little as $25USD. I've seen people I trust use the following site:
https://www.kinguin.net/category/22175/windows-10-home-oem-key/
I believe the best way to install would be:
1) Go to MS W10 creation site (link below), download and run tool (ideally with 8GB+ USB stick inserted) which should choose the correct version for your PC (make sure it matches what you buy)
2) Insert USB stick and boot to it (pretty sure you can run "setup.exe" from it from the desktop if you have boot issues)
3) *make sure to choose to KEEP APPS and DATA when upgrading unless you want to do a clean install. W10 is pretty good now at upgrading, and you can always clean install later if it doesn't go well.
MS media creation tool:
https://www.microsoft.com/en-ca/software-download/windows10
It may sound complicated but I've done this several times and it's worked out great.
Other:
If you do this, then decide to do a clean install (or upgrade W10 to itself to fix issues) you do NOT enter the key again. It gets properly registered with Microsoft.
Other:
I recommend using DDU to cleanup video drivers prior to the upgrade, then install new ones after.
http://www.guru3d.com/files-details/display-driver-uninstaller-download.html
Other:
I also recommend disconnecting your other HDD or SSD's to avoid accidental deletion of files. It's very, very unlikely though for upgrading but for a clean install it's possible to choose the wrong drive.