Having armed yourself at the Prepper Stash, you're now ready to head to the Outpost. As will become standard operating procedure, use your binoculars to tag the hostiles here.
You can tackle these guys any way you like. The kills don't count toward the 'real game' challenges, but you can earn a bonus $1000 by taking the place undetected. This is where your new bow comes in.
From the bluff above the camp, snipe the enemy. If anyone does charge up the path, use a tree or stump as cover to ambush them.
Kill them all to complete the objective.
Grab the map from the outpost, then Dutch will have you skinning up a radio tower, for old times' sake.
Throw the switch to complete Dutch's Island, and begin the game in earnest.
Note that there are other locations on the island. One is Johnson's Lookout Tower, which has a small amount of lootable ammo.
There is also an abandoned reaping truck toward the south.
Use the yellow control box near the back to open up the truck and loot the contents. There's a buck that tends to feed near here, if you're hunting.