The enrollment assistant for the Extended Security Updates (ESU) program for Windows 10 is rolling out gradually, starting with insiders. If you haven't received this feature yet, it may be available for your device in the coming weeks, possibly by the next 09/09 update.
Once it's available for your device, you can go to Settings > Update & Security > Windows Update. A link will appear to enroll you in ESU.
You can find other information and prerequisites at this link:
https://support.microsoft.com/windows/windows-10-consumer-extended-security-updates-esu-program-33e17de9-36b3-43bb-874d-6c53d2e4bf42