I always thought the parking brake was set to automatic by default. But this is all covered in pages 7-24 to 7-28 in your manual. If the brake force is maintained by the Auto Hold and you press P, then the parking brake will engage automatically. There are also 4 other conditions when the parking brake will take over from the Auto Hold.
The parking brake will disengage when putting in Drive or Reverse AND pressing the go-pedal.
The parking brake will disengage when putting in Drive or Reverse AND pressing the go-pedal.