How to update content catalog when updating local content?

27:00 mentions it is possible to update local content and the concept is crystal clear, but how do I actually update the catalog file? When all Adresses are set to BuildLocal & LoadLocal how do I tell the app to actually look for a Remote catalog somewhere?

 

You have to have some content remote when you ship the app. You can add new content to remote locations, but you cannot add new locations.