OTW Portfolio Light Lightbox image

I’m using otw portfolio light plugin a long time and i’m really like it.
Now i’m using it in my personal portfolio website.
the theme that i’m using has a portfolio section but i’m using otw for different kind portfolio in different page.

There’s not a problem about usage. But i really want to add a lightbox effect to otw portfolio light plugin.

After a lon search experience, i found this article
https://www.ads-software.com/support/topic/open-to-a-lightbox

after read the plugin author answer. I started to try change codes in php documents. but of course my php knowladge is not enough to do that

maybe author or other developers help me to figure out.

Here is my path;

i found code in otw-prtfolio-filterable.php

<?php if (have_posts()): while (have_posts()) : the_post(); ?>
                      <li data-type="<?php foreach(get_the_terms($post->ID, 'otw-portfolio-category') as $term) echo $term->slug.' ' ?>" data-id="id-<?php echo($post->post_name) ?>">
                          <article id="post-<?php the_ID(); ?>" <?php post_class('otw-portfolio-item'); ?>>
                            	<a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>" class="otw-portfolio-item-link">
                            		<div class="image">
                                		<?php if ( has_post_thumbnail()) { ?>
                                		    <?php the_post_thumbnail('otw-portfolio-medium'); ?>
                                		<?php } else { ?>
                                            <div style="background:url(<?php echo plugins_url( '/otw-portfolio-light/images/pattern-1.png' ) ?>);width:<?php echo get_option('otw_pfl_thumb_size_w', '303'); ?>px;height:<?php echo get_option('otw_pfl_thumb_size_h', '210'); ?>px" title="<?php _e( 'No Image', 'otw_pfl' ); ?>"></div>
                                        <?php } ?>
                            		</div>

when you click portfolio image, open in new page. but if i figure out to change link,page to image this gives me opportunity to open direct image and than apply lightbox effect by simple add rel=”lightbox”

I have to change this section of codes
<a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>" class="otw-portfolio-item-link">

in i have to add some codes in xxx to call portfolio image but i cant find how it’s gonna be.

as a said my php knowledge is not enough. waiting for your help