Together with your knights you besiege a castle defended by enemy knights. Choose a knight in the 'Inventory' and place it at the point of departure. From there it starts walking and you can launch it in the enemy's direction. Shoot your knight at the enemies to eliminate them and make sure he grabs bags of gold during his flight! When the knight reaches the end of the path, his parachute opens and he flies away. In the shop you can buy all kinds of items that will make the battle a bit easier for your knight.
Click there in the screen, where you want your knight to fly.