Since this is a spoiler topic, I will tell you but just to be sure, to get the answer highlight this blank space:you have to build a sewing hut. when you have a certain level of technology, a foundation for a sewing hut will appear for you to build on. This is one of the puzzles so for more info, check the guides section. BEWARE, it costs 5,000 tech points to change ONE villagers clothes Hope this helps.