When my Malibu is in park or in neutral, the RPMs run between 250 and 3. when my car is in drive or reverse the RPMs run normal. How do I adjust the high idol? where is this located?

There is no idle adjustment. That is controlled by the computer via the idle air solenoid. You can try cleaning the throttle body though. In fuel injected engines the throttle plate gets gummed up where in older cars it was kept clean by the gasoline flowing through it. Use any name brand carb cleaner that is marked "sensor safe" and spray around the perimeter of the throttle plate and also do that while running. After cleaning, it should run better. You can also clean off the cross wires inside the bore of the mass air flow sensor using a q tip and the same carb cleaner. Gunk buildup on the wires changes the way the sensor reads air flow.
Any questions about anything you don't understand, just ask.