How Do I Buy Things?
Got off my ship, went to the mercantile, clicked “I would like to see what you are selling” or similar, specifically the dialogue implied I could buy things. But once I get into the trade menu I can only sell things, not buy.
Top left has closed windows that you need to open in order to start buying stuff.
If you look at the bottom middle and bottom right they should have hotkey listings as to what they do.
One of them should be “sell”, as the default when you open a shop is “buy”.