There are a total of 8 settlements in the game, and they are the house/barn icon that appear on the maps. You must sail to each location to unlock it for future fast travel. Upon landing at each location, you will be given 2 or 3 objectives to take over the settlement. Examples of these objectives are: Kill x number snipers, Kill x number of offices, Destroy x number of poison caches, and Cut down French flag. Once you complete all objectives, you have captured that Settlement.
List of Settlement Locations per Area:
North Atlantic:
St. Anthony (593,-224)
St Johns (874,-633)
Perce (168,-406)
River Valley:
St. Nicholas (207,-765)
Greystone (524,-789)
Lock Cliff (801,-610)
La Bras-du-Seigneur (928,-279)
Coeur-de-l’hiver (454,-175)