Ace, there should be a knob located on the compressor with a gauge thats tied into it, turn the knob counter clockwise to decrease the pressure, and the opposite direction to increase the psi. the guage that is attached to the knob should indicate the regulated psi. you should see 2 guages, one for tank pressure, and one for regulated psi. if you don't see a device as discribed, then you may have to purchase one. they can be found at most hardware stores, Walmart, or Home Depot/Lowes. what type of compressor is it, a hobby compressor or industrial? What brand? later.