Office 365 login & Windows 10

Hi. I have a basic question. I have been using Parallels Desktop and a Windows 10 VM for a couple of years with a personal Office 360 account. About 6 months ago I upgraded to an Office 365 account via GoDaddy and let my Office 360 account transpire. Now that it has, I cannot figure out how to log into my Office 365 account.
1. How do I log into Windows 10 (the free Home edition) using my Office 365 account?
2. If I need to upgrade to Windows 10 Pro edition, how do I do that without being able to log into Windows?

Any guidance would be appreciated! Thanks.