Walk around and eat all the treats you find.
Kill bugs roaming on the arena.
Fight other Chompers using a weapon of your choice: ent’s branch, fish wand, devilish trident, banana club, royal scepter, carrot mace, and many, many more!
Eating and fighting give your experience which makes you bigger.
But be careful - single hit means defeat.
So use speed boost ability to run away.
You can also use it to chase for more food.