To get help from the Harvest Sprites, give each of them a lot of bread, which you can buy in the supermarket. The gnomes love bread. After you feed them, their heart points should rise to 3. You can now ask them to do your work (watering, taking care of animals, harvesting), or you can play a game with them. Do not forget to give them some bread each week (one piece for each) to maintain their heart level.