My train delivers trees to a wood mill which creates a lot of goods but the station doesn't collect the goods, so I cant transport it to the city. How can I fix this?
In order for a resource to produce, the station/dock/loading bay attached to it needs to have been visited by a transporter fitted out to carry that type of resource. In this instance, a goods transporter must have visited your station before it will start to produce goods.
Once that has happened, the resource will start delivering produce to your station (how much depends on the amount of wood you deliver there and your station rating).
This can be altered by the settings in the station window by changing Deliver cargo to a station only when there is a demand (under cargo handling) to Off.
A station accepts wood if it has one tile of the woodmill in its catchment area. If a station needs to get the goods in return from the woodmill you need to cover more tiles from the woodmill. I'm not sure how many exactly, but I think at least 3.
When you build a station you can see what the station will accept and what it will gain, make sure you have goods standing there when you build the station.