All you wanted to know about your Warehouse and were affraid to ask
Your Warehouse is placed in your city right next to the factories
All of your materials and products are stored in the warehouse.
To be able to upgrade your warehouse you require coins and a certain amount of population.
You can also remove the unwanted materials manually by clicking on the material where the button "remove" is located.
Population is shown in your upper bar together with coins and gems.
You can also see what population you need to be able to upgrade your warehouse to another higher level.