Read over the online applications for Italian citizenship for American citizens due to ancestry - the most popular. Print them out.
Reading them, you'll see that you need to dentify who in your lineage is going to qualify you, if you can qualify at all. It will also tell you what information and documents you will need to apply. For the rest of these posts, I'll call that person your QUALIFYING ANCESTOR.
You will notice that you need official copies. These are usually called certified copies, International Copies, or Apostilles. An apostille is a certificate that the signature of a public official (or an archivist) is authentic, in other words, that it is not a forgery. In your letters to archives and governmental agencies, you should mention that you are using the documents to apply for citizenship or dual citizenship. These people are usually trained to provide what you need, whatever term is being used. Expect to pay extra for this.
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