You get in the airplane from the front of the wing (opposite most low wing airplanes). If you look at some pictures of the factory prototype, you will see a small step mounted on the fuselage in front of the wing where you step first. There's also a step location on the leading edge of the wing where you can step and pivot around to make your third step on either the seat, or if you're really tall you can step all the way to the cockpit floor. At this point get yourself in the cockpit the rest of the way and lower yourself into the seat.
I did a bad job describing this, but if you look at the pictures of the plane I think it will make a lot more sense.