The quests to unlock the Train are available in the game starting with level 17.
You should see the quest “Call back Frank” appear at the top-left at level 17.
Finish it, and at level 19 you will get a call back from Frank (the phone icon appears at the right).
Get through the dialogue and you’ll get another quest, “Call the Town Hall”.
Complete this quest as well, and you’ll finally be able to repair the Old Way Station.
Get the nails (ask your friends or use RC), pine lumber, and oak lumber.
Plant oak trees and pine trees from the Shop > Trees menu.
Oak trees give you oak logs and pine trees give you pine logs. When you have oak and pine logs, open up your Craft Shack (if you don’t have one, buy it from the Shop > Buildings tab).
There, you can make oak and pine lumber from the logs you collected. Once you have all the lumber, click “Donate” in the quest menu.
After you donate the lumber, call the mayor to inform her that you’ve fixed your Way Station.