The cPanel accounts shared address book can only be utilized through Horde. You can retrieve the CardDAV URL in the Horde Webmail client.
- Log into the Horde webmail client for the e-mail address
- Hover over Address Books and select the Shared Address Book
- Click edit (the pencil icon) beside the shared address book.
- Copy the CardDAV Subscription URL for use in your CardDAV client