This turn you may be able to order production at more of your industries. You may also decide to expand one or more of these factories and mills to a higher capacity. Higher capacity permits a greater quantity of production each turn.
Click on the factories and mills to open the production dialogs.
These may be left open when you leave the screen, and can be relocated anywhere on the screen.
If you use items in one production dialog and later decide you want those items elsewhere you merely change your commands. The order in which you open the production dialog boxes is irrelevant.