Use the arrow keys to blow flames towards Katara, so that she can extinguish them with her water bending.
You'll sometimes need to blow flames into flammable objects, but do so strategically, or the fire will burn out of control and you will lose the avatar game.
Try to merge fires into eachother, it will save aang's airbending moves. Be warned merging four fire spots together results in a blazing inferno.
In adition to Katara, puddles and barrels filled with water may help extinguish fires.
