Hi,
To sign up for ESU, go to Settings > Update & Security > Windows Update. If your device meets the prerequisites, a link to sign up for ESU will be available.
Selecting "Sign up now" will begin the ESU enrollment process.
If you are signed in to Windows with a local account, you will be prompted to sign in with your Microsoft account. If you are already backing up your computer settings, you will see a prompt to register the device.
Please note that you must use a Microsoft account and must not have a work or school account configured in Windows.
If you have any questions, please specify them here.
Thanks.