I received mine when I purchased park tix at my AAA. You show it to the gate attendant at each park. Basically, it is right up front near the handicap spots. I loved it, especially after a long day in the parks. I didn't have to figure out how to get a sleeping baby on the tram. I just walked right to the car. In extremely busy times, it is possible for the spots to fill up however. It is just preferred parking. You still pay the $14 fee per day.
You need to check with your local AAA office - each one has their own policy for how they hand these out. Ours will only give them to you when you purchase a package from them.