Sequence 1 - Edward Kenway

Head to the ship's steering wheel and drive. Follow the in-game markers and shoot at the enemy vessels. Take out the 4 schooners first, then finally the huge frigate.

Bullseye

Upon taking control of Edward, swim to the beach and rendezvous with the Assassin. Chase after the assassin and once you find the viewpoint, climb it and synchronize with it. Viewpoints will reveal the immediate area and will allow you to fast-travel to them. You'll also see the collectibles and activities in the area revealed by the viewpoint. To do this, climb atop the first viewpoint, then press B to synchronize. You can go ahead and collect all collectibles in the area and once you're done wandering around chase after the target again.

Shortly after reaching the second viewpoint, you'll find the assassin who will still run away. Pursue him by running on and over obstacles until you reach an open area where he'll make his stand and fight you. Don't be too aggressive; keep your stance and use basic counterattacks to overpower and kill him.

The First Victim

You can return to the area revealed by the second viewpoint and start collecting the items there. Aside from the treasure chests, you can find a floating Shanty (song to be sung by your crew when sailing) and a Mayan Stelae (easy puzzles which will allow you to collect Mayan Stones - requirements for unlocking the Mayan Armor). Shanties need to be chased since they'll float away when you get near. The trick however is to know their fixed patterns and paths. Once you do, you can just take shortcuts and wait ahead of them. This is pretty useful especially when collecting shanties in cities.

The third viewpoint is on the tall waterfall. Synchronize with it to follow reveal the are and the last batch of collectibles. When ready, head down and enter the restricted area. Keep hiding under foliage and slowly make your way to the target, disposing off some guards along the way. Always use the stealth skill when you get near them or equip your bare fists first so you can knock the guards out if you don't want to kill them.

Approach the merchant after taking out all the enemies, grab any items around you, (including the treasure map and the buried treasure in the same area) then swim out to the ship located at the sea. Go to the bridge and take the wheel. Sail away avoiding any obstacles that may damage your ship and finally arrive at Havana.