Hello,
If you go to https://microsoft.com/software-download/windows10 for the Windows 10 ISO or https://microsoft.com/software-download/windows11 for the Windows 11 ISO, you can generate a download link on your own and then you can install Windows that way.
If you set up your PC with the Microsoft account that you bought the license with, your PC should automatically activate. If it didn't, check the Activation Troubleshooter at Settings > System > Activation.
Hope this helps.