The clock tower is in Diamond Plains, to the right of the section with the marshal's office and the saloon.
Diamond plains
in diamond plains
go to the train station
You oil it.
it is located at the diamond plains
After you oil the clock gears the clock will strike 3:00.
the gears in the clock tower
You go out the way you came in, just reverse
The oil can is used to oil the gears of the clock in the clock tower at Diamond Plains, so that the clock will work again.
the clock is in the tower. if you go all the way to your right they are doing construction and if you go inside theres the clock!
just play the game and you will find out.;)
you climb up and find the secret entrance