Click on General Settings and and click Application Settings. You see this:
Click the pencil icon next to iTunes to configure the server. Click Enable.
You can now serve up the contents of your Lacie 5big NAS Pro to iTunes clients.
Overall Conclusion: UPnP and Media Streaming
The Lacie 5big NAS Pro offers very easy configuration options. However, you can’t control what is shared via UPnP/DLNA; all data in the Public share is exposed. In addition, since you can’t extend functionality with a solution like Plex Media Server, transcoding is not an option here. If you can live without transcoding, which I suspect is most users out there looking for a streaming option, Lacie delivers a perfectly functional UPnP/DLNA experience, easy to configure and rock-solid as a DLNA server.
Stay tuned for the next update in the series!

Hi Jim,
Thank you for the in depth review of the streaming capabilities of this NAS. I am considering the purchase of this particular model and I was wondering if it is capable of streaming video to an apple tv. I currently have a qnap 219P II and am looking to expand my storage.
Keep up the good work!
Hello, I saw that the manual of the Lacie 5big NAS Pro does not list the m4a format among the itunes server compatible formats. Did you had any issue streaming this format?