One of the survival tips that Dennis mentions is utilizing the animals of the land, using their skins for crafting, as well as the plants. Get in the vehicle nearby and head towards the marker on your map. When you get to your destination, you’ll see some items on your minimap. The leaves are the plants you need to harvest, with the colors corresponding to the ones you need.
You will need two Green Leaves, one Red Leaf and one Blue Leaf. The blue one will be in the water, while the other two will be on land. Once you gather those, start searching the area for the boars. When you find them, shoot them from a distance until they fall down, then go and skin them. After getting everything on your list, open your map and fast travel to Amanaki Town.
Find Dennis and talk to him, which will prompt a little tutorial on crafting. All you need to do for now is craft two Medicines and then a Simple Rucksack. He will also show you how to learn some skills. You will have to get Takedown, but the other one is up to you (Cook Grenade is the better choice of the two available). Once you finish with that, you will get a call on the radio you stole in the beginning, so get in the truck and the next mission will begin.