Euphony has a separate File Manager application that you can use to copy data between your attached drives.
It has some standard file manager features where you can browse the library folder structure, select some amount of files and folders and copy/move them to the selected destination.

It can be accessed through Euphony App Main menu or directly using the euphony address and :8080 at the end, i.e.: http://euphony.local:8080/

It also offers some additional features that are mentioned on Euphony site but never really explained anywhere. 

CD Ripping

If you have a CD drive in your Euphony machine and you put a CD disk in it, the File Manager app will automatically show "Rip CD to Music" button. If you click it software will try to identify your CD by querying the online CD database. The result of this query will be shown (album and track info) and if the database returns multiple hits you may have to choose the correct album.
CD will be ripped to your Euphony Drive (/data/Music folder), songs will be tagged and cover downloaded if available. 

SACD ISO extract

This feature is able to extract songs from SACD ISO image file. It cannot be used to rip SACD media itself. 

It is activated by clicking on the file icon in the row of an SACD ISO image file.
A dialog will appear that usually displays basic file information but now it will also offer you an option to extract song files from SACD ISO image to Euphony Drive (similar to CD ripping).
If the ISO image file is contained in a folder and that folder contains some files you wish to preserve, you can choose to also copy those files to the folder where songs are extracted. 

Restart the Main Euphony App

In rare cases it may happen that Euphony seems to have successfully booted but you cannot access the main Web App interface.
To make sure that the boot process is finished properly, you can try accessing File manager application. Since during boot File manager app is started after the main Euphony Web app, the fact that the File Manager app is accessible means that the problem is solely in the main Euphony web application and not somewhere earlier in the boot process. 
As a last resort, you may try using "Restart Main app" on the top bar to try to start it and then attempt to access it again.

In any case, whenever that happens, even if you gain access to the main Web App by using this option you should contact support as this probably indicates some serious problem with your installation.