Station management
Automated station trading (via Manager)
Once a station is built or upgraded, it's production lines can work straight away if you manually supply materials but for it to really work for you, it needs a Manager. The Manger will begin to advertise Buy and Sell orders for wares using a budget that you can define the size of within the Manger's Detail Menu. Those trade deals may be fulfilled by NPC traders, your manual traders or civilian ships that you assign to the Station Manager (recommended to reduce the chance of a ware shortage stopping production).
Production Modules will often need multiple types of cargo (Bulk, Container, Energy and/or Liquid). Although the station will generate Upkeep Missions for missing ship types, as your stations grow you may need to invest in multiple ships covering the same type(s). Civilian ships come in Trade and Mine varieties, although the distinction is a little soft since both types can do fulfil both rolls with what they chose to do for a station being largely driven by whether they carry mining drones or not. See here for further details on Manager-controlled ships and about how to control where your ships will operate.