Turn off the power to the compressor unit from the circuit breaker.
Use the Phillips screwdriver to take off the retaining screws holding the air conditioner compressor cover in place. Carefully lift the cover off the compressor unit and set it to the side.
Flip the circuit breaker and turn on the air conditioner. Wait for the compressor to kick on. Observe the fan and other moving parts of the compressor. Specifically look to see if any specific parts are moving erratically or more than other parts.
Turn off the power to the unit and, using a socket set or an adjustable wrench, tighten any bolts to parts that seemed to move excessively.
Have a helper pull the compressor to one side. Set the dampening foot pads down in place where the compressor foot will rest and then set the compressor down on that side. Pull the compressor upward from the other side and set the dampening foot pads under those feet.
Replace the compressor cover and the retaining screws with the Phillips screwdriver. The addition of the dampening pads should significantly decrease compressor vibrations.