Information for foreigners intending to come to Italy can be obtained through the official website of the Italian Ministry of Foreign Affairs. Please check if a VISA is requested for foreigners coming from your country and follow the instructions of the Italian Ministry.
In order to obtain an invitation letter you need to register online. While processing your registration please tick on the appropriate box to ask the issuance of  the VISA Invitation letter. You will receive it by email only once the payment will be finalized.