Firstly you would need to look at the Language Description
Top Sony - Languages Description
Look for Italian - which is EUROPE_5
To flash your phone you will need XS++
Here:
XS++ 3.1 Guide-Flashing,Customizing,Recovering - Top Sony Forums
This shows how to use the program.
Thirdly you will need the files from the download section of the website:
Downloads - W580 - Top Sony Forums
Since you want it unlocking, you want the Generic EUROPE_5 MAIN and FS file, you also want the custom files.