For the last part in the France campaign you need to complete a treasure map requiring eight steps. You need to use the Captain John Hawkins when going to the areas to collect the pieces.
Clue 1: The outlet of the river west of New Orleans
Clue 2: From Cartagena's coast go south
Clue 3: Easternmost point of Barbados
Clue 4: Northwest coast of the island of Port Royale
Clue 5: Bay south of Cahuita
Clue 6: In a bay across from Port of Spain (There is a shipwreck on a rock if you zoom all the way in
Clue 7: End of the narrow bay between Belize and Valladolid
Clue 8 North coast on the island north of Coro
Treasure location: On an isle between Nassau and Cat Island
Once the captain reaches the treasure the achievement will unlock