Hi Mircea,
You can’t add article excerpt in slides. We have designed our theme this way. It needs code customization. To add this feature in theme is a completely new feature in this theme.
Go to theme folder -> inc -> functions.php on line no 149 you will see below code
$wowsome_featured_sliders .= '<div class="featured-title"><a href="'.esc_url(get_permalink()).'" title="'.the_title('', '', false).'">'.esc_html(get_the_title()).'</a></div><!-- .featured-title -->';
replace it with
$wowsome_featured_sliders .= '<div class="featured-title"><a href="'.esc_url(get_permalink()).'" title="'.the_title('', '', false).'">'.esc_html(get_the_title()).'</a></div><!-- .featured-title -->'. esc_attr(get_the_excerpt());
We recommended you not to change the code but if you change the code then while updating to new version all your customized code will be lost. So better make a child theme and customize the code. If you make direct code changes then while you update to new version the same changes need to be made from your end.
Thank you!