First, you need to download Windows 10. You can download it directly from Microsoft, and you don’t even need a product key to download a copy.
To download Windows 10 ISO file from Microsoft you read this article: https://saleproductkey.com/windows-10-free-download-from-microsoft-trial-version/
After you have Windows 10 ISO file, you can use it to install windows 10 on your pc:
In this step, Windows will ask you product key. You select “I don’t have product key”
After you select this option, you will be able to install either “Windows 10 Home” or “Windows 10 Pro.”
After you install Windows 10 without product key, you can enter product key to activate it.
You go ” Setting => Update and Security => Activation“
Then you click “Activate Windows now”