How should I write a story to do with the Italian Mafia?

You have to do research on the Mafia -- writers spend about half their time doing research and the other half writing what they've learned! Look up everything you can find out about the Mafia -- what is it, who is involved, when and where did it start and what goes on within it. Then think of how the Mafia is going to come into your story, what conflicts it will create and what problems for the characters, how it is going to end up (will the Mafia win or lose), what does the character do within the Mafia or against it.