You need to enable “ID Sharing” in the extensions capabilities in the console.
Then ask the user using your extension to share their ID with the extension
Example: GitHub - BarryCarlyon/twitch_profile_extension: A simple Twitch Extension to cover the basics of using the JWT and EBS together to get Twitch API information
See also: requestIDShare() under helper: actions - Extensions Reference | Twitch Developers
The customer support guide refers to streamers adding/removing extensions from their channel, and/or users revoking access, not directly for users using extensions. So you ended up in the wrong part of the documentation/support
On a panel extension the “dude” icon can also be used, the “shareID” (in this example) button invokes requestIDShare
On video this is behind the taskbar in the “manage access” button
