Howdy! It looks like Featured Image support was added initially, but the theme doesn’t actually use Featured Images anywhere. We’ll remove this support in a future release — thanks for bringing this to our attention.
If you want to add support for post thumbnails, first you’d want to create a child theme, then copy any files you want to change from the parent theme to the child theme (probably the content-*.php files), and use this line of code to display the post thumbnail wherever you’d like in the template:
<?php the_post_thumbnail(); ?>
Once we update the theme, post thumbnails support will be removed. You can re-add it in a new functions.php file in your child theme:
quintus_child_post_thumbnails() {
add_theme_support( 'post-thumbnails' );
add_image_size( 'my-post-thumbnail', 300, 400 ); //Set the desired width/height
}
add_action( 'after_setup_theme', 'quintus_child_post_thumbnails' );
Then style the post thumbnails you’ve added accordingly in your child theme’s style.css
I hope this helps!