You have to have the Diamond Pass from AAA. If you buy your park tickets at AAA, they will sometimes (but not always) give you one - if you buy a package there you will for sure get one. However, they do not always allow you to use it at the Disney Parks. If it is a super crowded day/time of year, they will direct you to regular parking. I had a Diamond Pass last year at Easter, and was not allowed to use them at any park.