To be precise: You'll want to consult a repair manual specific to your 2002 Buick Rendezvous (either a Haynes or Chilton manual, or a digital equivalent). These manuals have diagrams and precise instructions that will show you exactly where the sensor is located on your particular vehicle's engine. The engine might have slight variations depending on the exact engine configuration.
Simply searching online for "2002 Buick Rendezvous crankshaft position sensor location" might also yield images and videos that can help you visually locate the sensor. Remember to be cautious when working under the hood, and disconnect the negative battery terminal before starting any repair work.