OK, we're getting a little complex here. You have to "destroy a tower". Oooooo. Get the food, gold, wood, and build your normal buildings - mill, dock, lumber mill, houses. Build lots of villagers to gather everything up for you. They teach you about the garrison bell which is a great improvement over AoE. The blacksmith helps you enhance your weapons. Go kill the tower!

Age of Empires II Walkthrough