Start with but a fly and evolve your way to become the biggest and badest creature on the map. But take heed, there are creatures out there that will eat you before ever being your friend.
Follow the directions on the hud to tell you which "food" items you have to hunt down, and then munch munch munch.
Fly with either the mouse or the WASD keys.
If you find a good position you can feed in relative safety, but when the goings get tough, you can hide in bushes or clouds.