Hold down Lock-On with Pandora Equiped.
Then, go through the directions clockwise, quickly.
Right, Down, Left Up (or one circular motion on the movement stick)
This will transform Pandora into a Rocket Launcher.
Then, go through the directions clockwise AGAIN, quickly.
Right, Down, Left Up (or one circular motion on the movement stick)
This will turn her into the Revenge Laser.
If you are having trouble figuring out the keys look in the control set up to determine where the movement keys are...although, you should know if you have Pandora.