To the media page add the following template text:

{{PD-Italy}}

If the media page already contains {{Information}} you may alternatively add the above template text to the "Permission" field as in the following example from File:RNLittorio.jpg:

{{Information
|Description=RN ''Littorio'', high speed manoeuvres, summer 1940.
|Source=Ministero Della Difesa-Marina
|Date=''circa'' 1940
|Author=An unknown serviceman of the Regia Marina
|Permission={{PD-Italy}}
|other_versions=}}