To develop the building, select the palace in the center of the kingdom. No Kingdom can be developed without leveling up the palace. Palace - use a hero to increase the building development rate. Point bonus - the INT of your hero will affect the development bonus. Be sure to claim your quest completion rewards. The farm can be leveled up at the land office of the Kingdom. The production volume of the kingdom will increase as the farm levels up. Food is mainly used for the production and healing of troops but is also used as a resource to upgrade certain buildings. More gold, food, and metal resources cna be gained as the land office level goes up. The resources produced in the kingdom are stored in the warehouse. But be very careful it doesn't get too full because the resources will be automatically discarded when the number of stored resources has reached the limit. More resources can be stored when the warehouse levels up.