To use the Content Server with RDP-Calibre goto preferences -> Sharing overt the net.
enable "Requre username and password" and "Run server automatically" then "Start Server"
Create a user and make sure they have write access
Check your Docker Settings to see what IP and port you used for the :8081 port mapping.
Goto Lazy Librarian and setup the Calibre Settings to use the Content Server.
Now when Lazy Librarian processes a book it will use the RDP-Calibre to do so, which will automatically update the book list to include the new book.