You must win all five prize fights. During the fight, you are limited to your fists or melee weapons. As your opponent will only use their fists, using a melee weapon gives you a much appreciated edge.
The fights are located in the following areas:
Little Italy - 2nd floor of Molsenni's - Prince Street and Bowery
Brooklyn - 1st floor of Pitkin Garments - Washington Street and Front Street
Midtown - Basement of Corcoran's Perch - 23rd Street and 4th Avenue
Hell's Kitchen - Roof of Stromboli Supplies - Galvin Street and 11th Avenue
New Jersey - Basement of Highway Hotel - Observer Highway and Newark Street.