The Italian international midfielder, 28, recently signed for the Hammers on a deal until the end of the season.
"I am very happy because it's a very, very important experience for me, playing for a very traditional and historical club such as West Ham. It is a great honour," he told the club's official website.
"When I realised how big the fanbase is and the traditions and very, very important history that the club has, I was more than happy to come to England.
"A lot of the traditions of the club, I learned from the West Ham fans who are already there in Italy."
West Ham return to Premier League action on Wednesday night when they travel to London rivals Chelsea.