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Once a station is built or upgraded, it's production lines can work straight away if you manually supply materials. However, for it to really work for you, it needs a Manager and ships assigned to the Manager (see below). 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 manually-controlled Traders / Miners or such ships that you've assign to the Station Manager (recommended to reduce the chance of a ware shortage stopping production).
Player-owned Warehouses from the HoL DLC are a little different. Things on this page apply to them too but they also have a few additional notes described here.
Station construction
Stations are build by Construction Vessels (CVs), which are sold by XL Ship Dealers and can only build the sorts of stations that are found in the system that the CV is built in. The CV needs an Architect NPC (and also an Engineer for repairs and a Defence Officer for weapons control). Once construction of a station is begun, you can technically cancel construction but it's better to make sure you want to build it in the place to begin with rather than risk the possibility of something bugging out with the CV and/or Architect.
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