Sorry, I was a bit vague with that one.
When trading, the ships or wagons have to go to either the admin centre or a trade dock, or a Tradehouse. I just thought the Warehouse could double as a way to receive resources from the coast without having boats or putting your admin centre on the shoreline, or as a way to receive resources from anywhere on your borders without having a massive surplus of people with wagons.
Thanks Shawn.
(P.S. is there a more multi-mod compatible way to add resources to the game, like through mutators?)