How do you adjust parking brake 2008 Toyota Highlander?

It is supposed to adjust automatically (from constant usage). If you don't ordinarily use the emergency brake the adjusters might be 'frozen' from dis-use. On an empty parking lot try putting the vehicle in reverse and while keeping a steady foot on the accelerator, back up SLOWLY but steadily and with your left foot pump the brake pedal a few times. If this doesn't work - try doing the same thing only this time pumping the emergencybrake pedal. If neither of these tricks work, you'll have to see your mechanic and get the mechanism freed up.