Display recent posts from portfolio

You can get latest post from any post type with the simple query

<?php
// Arguments
$args = array(
    'post_type' => 'portfolio',
);

// The Query
$the_query = new WP_Query( $args );

// The Loop
if ( $the_query->have_posts() ) {
    echo '<ul>';
    while ( $the_query->have_posts() ) {
        $the_query->the_post();
        echo '<li>' . get_the_title() . '</li>';
    }
    echo '</ul>';
    /* Restore original Post Data */
    wp_reset_postdata();
}

Or if you want show latest portfolio posts in the widget, you can use the below plugin:

• https://wordpress.org/plugins/recent-posts-widget-extended/
• https://wordpress.org/plugins/recent-posts-widget-with-thumbnails/
• https://wordpress.org/plugins/flexible-posts-widget/