Styling Related Custom Posts

I created a related custom post using WP Show Posts and an element hook.
I need to know how to style the output.
I am using the Dispatch site as a basis, and would like to apply the following classes (wpsp-card, zero-padding, no-background) similar to the standard sidebar from dispatch.

I created a list based on my custom post type and taxomony in WP SHow Posts.
I then created a related event query using a, Element hook which displays the WPSP list just above the right sidebar.

Where do I reference/apply the classes I want to style the related sidebar posts? DO I need to create a shortcut to apply them?

Here is my coding from the Related-Event Element:

<?php
if ( is_singular('event') ) {
$cats = get_the_terms($post->ID, 'event_category');
$cat = $cats[0];
} else {
$cat = get_the_terms( $post->ID, 'event_category', get_query_var( 'event_category' ) );
}

$cat_slug = $cat->slug;
$list = get_page_by_title( 'eventrelated', 'OBJECT', 'wp_show_posts' );
wpsp_display( $list->ID, 'tax_term="' . $cat_slug . '"' );

?>

Thanks for your help.