By clicking on a city's node, you can access production workshops you own, to assign workers to produce items from materials placed in your warehouse. You will also see which production workshops are currently in use, as well as total progress. If your workers create items once your warehouse is full, it will place the items in anyways, and prevent you from depositiing anything until you clear out free space.
Using Production Workshops
Click on the production workshop you wish to utilize to start.
1. Select the item to craft. 2. Select the worker to craft the item. 3. Assign the amount of times you wish the worker to produce the item. 4. Click the start button at the bottom.