Use Quick Search to search the catalog. In this example, the search will be for Berlioz's Symphonie Fantastique. After you search, use the box on the left of the screen to refine search by Format Audio.
Some records will have a box stating "View Record in Naxos Music Library." Click that to be brought straight to a recording in Naxos. You will need your Duquesne Multipass ID if you are accessing it off campus.