Upvote:2
It's a two-step process and you should allow additional time at the airport to get it done. Before you check in for your flight, go to the Customs desk. You'll need your completed tax free form, passport, and what you purchased (unused and, as appropriate, sealed). The separate receipt the merchant gave you, the fattura, has to include your name and the tax (IVA). If there are spaces on the fattura which you are meant to complete, make sure you correctly fill in that information (ask, if you're unsure).
Next you go to a refund office, present your Customs-stamped forms, and receive the refund, either in cash or on your credit card.
At Malpensa, there are four VAT refund desks: Global Blue, Tax Refund, Premier Tax Free, and Forexchange, all located in Terminal 1 and all with two locations, one on the first floor in departures boarding areas A, zone 12, the tax free area. Be aware that there may be an administrative fee charged.
Several notes: you don't indicate from which airport you are leaving, thus the Malpensa information. Some of the above refund services may have offices in the city, and you could get your refund there. You still have to have Customs validate the form (at the airport) and return the form to the service; if you don't, the refund amount is charged to your credit card.