Answer: First, you need the recipe for the shrinking potion. Follow the game objectives and complete them. After you have saved the Wizard from Grim mountains, you will receive a letter from the Caretaker. The letter contains the recipe for the shrinking potion. Once you have the recipe, find cauldron. There is one in the Castle Kitchen and Tavern in the Sky. Prepare the shrinking potion there. Go back to the Storage Room with a note about Barrel Town and tap the 'Drink the shrinking potion' button. Please note. You can only shrink at the Storage Room.