The supplies in your castle are not in order. Fortunately, the trading boat comes by so that you can buy the stuff you need. To make money and to get rid of things you dont want, you sell to the boat. You also get money if your opponent buys something from the boat you placed on it.
After 3 turns - its a new trading day, the rooster crows - you get new stuff in your castle.
You can play this game with different variants. From very easy to very challenging.
Play the "Good Stuff" game and you win by being the first to get everything right in your castle.
Play the "Richest King" game. All coins and value of the items in the castle are added up. The winner is the richest player.