Answer:
Food, water, shelter, and fire
Explanation:
First and foremost, build a fire before sundown or you'll die from the cold and can't cook food like fish or meat.
You can get by food by either getting coconuts and fishes. Explore the island for fruits and vegetables and hunt for wild animals.
Find a good source water by finding a river or stream.
Build a shelter by either sticks, woods, or large tree leaves. You can also find a cave so you won't have problems from strong rains but you need to explore it first.