Usage

Download source files and place them into CKeditor's plugins folder.
Define plugin in CKEDITOR config object.
CKEDITOR.config.extraPlugins = 'lightbox';
Add lightbox button to your editor toolbar anywhere you like.
CKEDITOR.config.toolbar = [
   {name:'links',items:['Link','Unlink','Anchor','lightbox']}
];
Set your CKEDITOR language to 'en' or 'pl' if you did not set it yet.
CKEDITOR.config.language = 'en';
Download and install the latest version of Lightbox.
Add code from below to your website source code:
<script>
$(document).ready(function(){ ckeLightbox(); });
function ckeLightbox(){
    var c=0;
    $('a.ckelightbox').each(function(){
        c++;
        var g=$(this).attr('class').split('ckelightboxgallery')[1];
        if(!g)g=c;
        $(this).attr('data-lightbox',g);
        $(this).attr('data-title',$(this).attr('title'));
    }); 
}
</script>
Done.
Rate or add comment if you enjoy.