If you registered for an upgrade you shouldn’t have an issue, use the media creation tool from https://www.microsoft.com/en-us/software-download/windows10 Take a look at this link for step by step instructions.
“You’ll be asked for the product key after the process is finished. Just click “Do this later” to skip this part and continue the setup process.
After you log into your new, clean-installed Windows 10 system, it should automatically activate itself after you connect to the Internet. If you took advantage of the free upgrade offer, it does this by checking your computer’s hardware and then checking in with Microsoft, verifying that your hardware configuration is authorized to use Windows 10.”