This quest is quite terrible at instructing how to do this. I was able to fight through figuring out how to visit the nearest town but once there I could not buy any stone. It claimed that my army or town was too full even though I had sold everything in my army. I had to keep one cow because it said I had to.
SO frustrated, I moved my army back to my town. On the way, my gold vanished due to something called "Gold deterioration" or some such nonsense. MY army did not enter my town and there is no icon letting me instruct it to do so like there was for the town I visited.
SERIOUSLY there is a lot of work needing done on this game.
please tell me how to do this quest before I finally decide that the developers are nuts and I go back to a competent game like Stronghold Crusader. Thanks.