Ganesh,
If it is cranking when you push the button, you are sort of half-way there.
Now you need to have the ignition switch (key switch) wired to provide power to the coil when the key is turned to "On". Another complexity is that the foot-starter switch might have a small post on the side that would be wired to the coil (to give 12v to the coil while the starter is cranking).
In a 12v system you need to have a ballast resistor in-line from the key-switch to the coil or you need a coil that has an internal ballast resistor. I do not know how to determine if you have a coil with an internal ballast resistor (without a ballast resistor, the truck will start but you will burn out the points in short order).
Is this confusing enough?
