On iPhones you are able to activate and deactivate your local files and Audius. This allows you to limit the app to only retrieve music from either Audius, Your Local storage or both.
In order to access the library management screen first click on your user icon at the top right hand corner.
Then click on the Library menu item.
Then a pop up will appear allowing you to enable / disable Audius and access to your music files if any are found stored on your iPhone.