you need low density rail roads with places that have ores, but this is not the part where you get the resources though.

Now you have a railway (here's a tip: unpaved roads don't let you expand the outcome).ok, let's get back to the subject, to expand the outcome, click on the ore, and you will see expand outcome option, and after 5 turns you will start to receive the ore.

You can get even get more resources from an ore by upgrading the railroad, then click expand outcome.

If you want your resources to be used in a certain town, just make a railroad path from the ore to the city.