Hi ilGabry, this is Kimberly, an independent advisor. I'm glad to assist you today.
There are two main categories:
Commercial/Enterprise Customers:
These can purchase ESUs directly via Volume Licensing (VLSC, CSP).
Home and Small Business Users:
Microsoft announced that certain consumers using Windows Backup may get ESUs for free.
Since you mentioned, you already use Windows Backup, possibly you're already enabled for extended support.
If you're a home user with a PC using Windows 10 Home or Pro and have the Windows Backup app installed from the Microsoft Store, you may automatically be enrolled to get free ESUs.
However, Microsoft hasn't been fully transparent yet on how this is detected or confirmed on your PC.
Should you have more questions, please let me know.
Best regards,
Kimberly