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.
You will get the Nails as Gifts, and you need to get a hold of some Pine Lumber and Oak Lumber.
You can buy the trees from your Shop > Trees menu. Oak Trees give you Oak Logs and Pine Trees give you Pine Logs.
Once you have Oak and Pine Logs, open up your Craft Shack (if you don’t have one, buy it from the Shop > Gear tab) to make lumber. When you have all the lumber, click the green “Donate” in the quest menu.
After you donate the lumber, call the mayor to inform her that you’ve fixed your Way Station.