click on any empty tile on the left side of your town it will list the buildings that you are able to build in the list will be manor, barracks, infirmary, workshop if you have not build it already and lastly the war bloc, click on war bloc and you will have the option to build it on the empty tile, you can not build it on the right side of your town on an empty tile where the farms, lumber mill, stone and quarry and iron mines are.