I've a catalog of my CDs. Recently I've copied a lot of tracks from my CDs to USB hard disk. How do I associate the location of the tracks on the hard disk with an entry about the CD in the catalogue?

If I execute Album>Add media files and point to the USB hard disk I get a duplicate entry in the catalog for every CD I've copied.

Is there a way to just add location of track files to the existing CD entry in the catalog?