How to set the timing on my vehicle

What do you mean "not right"?

Steps - Start engine, let it warm up, snap the throttle a couple times.
Connect the timing light and verify timing is at 15 degrees TDC.
If not rotate the distributor to correct it.

Now this assumes the engine is running good to begin with and that the harmonic balancer is still in good shape, the rubber in them can break loose and allow the outer ring to slip, which makes the timing marks useless.

To check for that bring cylinder number one up to TDC with the spark plug removed and put a dowel or similar in the cylinder and fell for the point where the piston stops moving either direction. That will be TDC. Now look at the location of the mark on the balancer. If it is on the zero mark it is okay.