Where do you have to go to find a way to Havana on assassin's creed iv black flag?

In Assassin's Creed IV: Black Flag, to find a way to Havana, you need to visit the island of Nassau. After completing certain missions, particularly those involving the pirate life and gathering information, you will receive a quest that guides you to Havana. Look for clues and interact with characters who can provide further directions to reach your destination.