The train will not arrive at the Diamond Plains station (right side) until you repair the rusty clock in the Clock Tower.
You first have to catch the girl's calf (left side of Rock Ridge) and bring it back to the ranch. She will give you a saddle, and back at the Trading Post in Dusty Gulch you can trade it for a gold pan or an oil can. Ideally you get the gold pan first, and then swap that again for the oil can. This allows you to pan for gold using the map you can win at the Casino in Dos Cactos. You use the nugget to buy potions from the peddler in Rock Ridge.
Once you have the potions, swap the gold pan for the oil can and enter the clock tower. Oil the center section of gears only, and the clock will be fixed. The train will arrive at the station. (You may need one of the potions, the Concentration Carbonate, to defeat the train robbers, which is why you used the gold pan first.)
only when your doing the train robbery
go to the bank
go to the train station
you shoot them so none of them reach the front of the train
Diamond Plains
I don't know, they're asking you.
The kid with the big head is in Dos Cactos in poptropica wild west island. He is near the sign that says: Train, Shooting Contest.
you leave before the bandits kill you
They go in a train tunnel in the middle left
It will be after the train robbery.
I think once you start riding the train it will tell you instructions and then you just do what it says.
its on the right of the train station in rocky ridge