Recently put firefly on my WHS too. I’m no expert.
I pointed firefly at D:SharesMusic (rather than d:shares)
Then I think you need to do a scan – I used remote destop to access the firefly tray config icon on the desktop of my headless WHS.
The tray config is great for displaying logs about what firefly is doing
Then open the web interface (from the config window) and you can force it to do a scan. Should see something like ‘added 123 songs to library’
Think you are probably really close as your itunes have found firefly.
good luck