How to add a class to a specific image link?

I am using the avia layout builder and need to add a class to an image link. After researching in your forum I created ‘config-templatebuilder/avia-shortcodes/image.php I also added the following code to my child theme’s functions.php:
add_filter(‘avia_load_shortcodes’, ‘avia_include_shortcode_template’, 15, 1);
function avia_include_shortcode_template($paths)
{
$template_url = get_stylesheet_directory();
array_unshift($paths, $template_url.’/shortcodes/’);

return $paths;
}
So, How to add a class to an specific image link?