When you spawn, there is a waterskin on a rock next to you. Make sure to pick it up. (You can also craft it later)
Proceed north to reach the river. Your position will show up on the map by now.
Dont forget to invest your character points and recipie points.

How to feed yourself:
Steal turtle eggs. They are in nests on the beach.
Loot plants with E and eat the bugs you get occasionally.
Put fiber and seeds in your campfire to produce a simple soup.
Kill rabbits or deer and harvest them with your weapon to get meat. (pickaxe for hide/bones)
Cook the meat in a campfire before eating.

How to get food poisoning (aka things you shouldnt do):
Over-eat yourself
Eat rotten food
Eat raw food

But: if you just started to starve, feed yourself on a piece of raw meat if you have nothing else with you. It will probably drain 1/4 of your health, but at least you have some more time to get yourself some bugs.