there is a output pin to goes to the arduino digital pin and a vcc and a ground pin.
So, connect the Vcc pin to 5V (or 3.3.V), connect Gnd to Gnd, and connect the output pin to a digital pin. Then, digitalRead() that pin to determine if the PIR sensor is seeing motion.
Only when you can reliably detect motion would you add code to ramp up, stay up, and ramp down. Put all that code in a function called motionDetected() that you call when there is motion detected.