Kenway's Fleet is unlocked early in Sequence 4 in Assassin's Creed IV Black Flag
It is a metagame which will help you gather resources and reales
To access the Kenway's Fleet Interface, visit the Captain's Cabin below the Jackdaw's wheel, and interact with the map on the table.
In the main game, you can attack and board ships, and then Capture and Send to Kenway's Fleet
In the Kenway's Fleet Screen, you can manage your vessels and conquer trading routes via ship battles, and complete and secure trading routes. This gives you Reales which are transferred to the main game and can be used to upgrade the Jackdaw
You can also send your fleet on trading missions and get resources such as Treasure Maps
