The volume control is the "thingy" directly behind the knob that you turn to change the volume. As stated, likely it will be necessary to take the radio apart to get to the volume control. The product has to be spayed INSIDE the control to do any good. Spraying on the control is just going to risk ruining the radio.
A typical volume control looks like this. See the holes in the control? The aim of this is to spray/clean the resistor and contact slider inside. http://www.radioshack.com/product/in...ductId=2062359