Hmmm, that answer didn't seem to be too clear to me, so I'll give it a go
If the handle is left in the unlocked position, the brake pedals work just like a car. Push the pedal to operate the brake, the harder you push, the more braking you get. Take your foot off the pedal and the brakes are off.
With the park brake handle out and turned 90 degrees to lock it, pushing on the brake pedals applys pressure to the wheel brakes, and this is trapped in the system, so when you take your feet off the brake pedals, the brakes remain on. Pumping the brake pedals increases the pressure held in the system.
To release the parking brake, twist the park brake handle 90 degrees, and tap on the left hand brake pedal, from either seat. The park brake handle should retract on its own when you do this.
I can't comment on the powered brake, as I haven't seen it.