Animating image sequence with button?

Over the past couple of months I have been working on getting RFID to load multiple images with music, I have that working. Now I just want a way to go through the images, and I was looking at using a button to do this. I'm not sure how I would include it in my arduino code that is sending serial data to the RFID and also adding the code into the processing code?

Thanks

I suggest you start by deciding how the new messages are going to be handled over the communications interface between Arduino and processing. Then design and implement code on the Arduino to detect the button press and inform the Processing application using your new communications protocol, and code on the Processing side to receive the notification and carry out the corresponding action.