To edit a song's info in your File Library you must first log into your eMastered account, and navigate to the "My Library," section from the top-left menu.

From here click on the song's name that you wish to edit, and click on the pen and paper icon to the right side of that track:

From here you can edit the song's name, artist's name, album, and even add track artwork. To confirm your changes click "Submit," at the bottom of the popup.