The clock tower is in Diamond Plains, to the right of the section with the marshal's office and the saloon.
Diamond plains
go to the train station
in diamond plains
it is located at the diamond plains
You oil it.
After you oil the clock gears the clock will strike 3:00.
You go out the way you came in, just reverse
the gears in the clock tower
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!
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.
just play the game and you will find out.;)
you climb up and find the secret entrance