Add in the lightbox extra class here :
![](https://ticksy_attachments.s3.amazonaws.com/5001797742.png)
and the JS in here
![](https://ticksy_attachments.s3.amazonaws.com/6031965862.png)
For 1st Button use this code:
jQuery( document ).ready(function() {
jQuery(".lightbox .button:first-child a").attr("rel","prettyphoto");
});
For 2nd Button use this code
jQuery( document ).ready(function() {
jQuery(".lightbox .button:last-child a").attr("rel","prettyphoto");
});