I parked there for a different cruise line. It's outdoors, with a booth. You get a ticket and pay on the way out.
Don't panic when you see the line to park! It's very well organized. I was directed to a bay where I dropped off my checked bag, then was directed to the parking lot. Someone I know was behind me, and she went directly to park - we walked to the ship together, as I arrived within a minute of her parking.
The whole procedure, including walking back to the ship, took less than 5 minutes. Boarding was a different story, but perhaps Disney has a better system. :lol:
Yoda has much better info about the parking itself. But my statement that it looks like a madhouse as you drive up, but is quickly sorted out, still stands.