Within 3 months of arriving in Italy, non-EU family members of EU citizens must apply must apply for a non-EU family member's residence card from the main police station (questura) in the place where they are living.
The documents you need to obtain a residence card for your non-EU family members are:
a valid passport or equivalent
a document from the relevant authority in their country of origin or the country where they have come from, proving that they are part of your family and, if required, that they are: dependent, part of your nuclear family or a family member with serious health issues.
proof that they have applied to register as a family member of an EU citizen
four identical passport photographs of the non-EU national
documents proving the existence of a stable relationship with you (as an EU citizen), if the application is made by your partner
proof that you have applied to register, even if you are an Italian citizen returning to Italy from abroad.
To prove that your family member is dependent on you, you will need a certificate to that effect, issued in the last six months by the relevant authority in the country you are coming from.