After the previous mission, you will appear on the island just south of Vaas' island. Before jumping in the water, use your camera to tag the one enemy standing on the docks, then head over there. Use a Death From Below takedown on the previous enemy, then head onto land. Follow the path until you get to two enemies abusing some native, so sneak behind them and kill them both.
Approach the compound, being careful of the sniper in the tower on the right, as well as a guard and two dogs in front. If you have the bow, use that to kill them, as well as two more guards that show up. Head to the wall of the compound and follow it to the left, until you find a rope that you can use to climb. Don't worry about the enemies seeing you through the fence, as they can't.
There's a door next to the fence that you can go through, which will lead to a room with a bunch of TVs. The surprise is that Vaas knew you were coming and has set fire to the building. Run through the door and you'll fall through to the floor below. Head around the corner and climb the ladder to the roof, where you'll find a lot of enemies on the ground below.
Your first priority is to get off the roof and onto the ground below, as the fire will spread on the roof and only hinder your progress. Use cover as best as you can to take out all of the enemies that come towards you. As you approach a large set of doors, a Heavy Gunner will appear, so use any Molotovs or just shoot him in the head.
Go inside the building and Vaas will end up stabbing you around the corner. You're now in some kind of hallucination, so just walk forward until you get the prompt to shoot. In the next section, just keep shooting the illusions of Vaas as they come until you get to the end, where you will do some QTEs to end up stabbing Vaas. After some cutscenes, the mission will end.
