Hi Ellen,
Thank you for contacting Styled Themes support team. To change the order of portfolio post of Sleeky Recent Portfolio widgets you need to do certain customization on sleeky_latest_portfolio.php[ site_folder\wp-content\themes\sleeky-pro\sleeky_includes\widgets\skeeky_latest_portfolio.php ]. There you need to change wp_query argument to something like this:
$args = array( 'post_type' => 'portfolio', 'posts_per_page' => 6, 'paged' => $paged, 'order' => 'ASC' );
Note: As this widgets file is not template file , you can’t customize on child theme . To customize on child theme you need to create another widgets. So you changes will not lost on theme update.
Let us know how it will goes,
Thanks