if ( have_posts() ) :
    while ( have_posts() ) : the_post();
        // This inner part of the Loop varies by theme
        the_content();
    endwhile;
endif;

<div class="row container">
    <div class="left column">
        <?php
        // Your standard Loop goes here
        if ( have_posts() ) :
            while ( have_posts() ) : the_post();
                // Format as desired
                the_content();
            endwhile;
        endif;
        ?>
    </div>
    <div class="right column">
        <?php
        // This is where you create an additional Loop
        $args = array(
            'post_type' => 'post',
            'category_name' => 'your-category', // change to your category
            'posts_per_page' => 5 // change to the total you want to display
        );
        // run the query
        $thirdLoop = new WP_Query($args);
        // Now this looks mostly like a normal Loop:
        if($thirdLoop->have_posts()):
            while ( have_posts() ) : the_post();
                // Format as desired
                the_content();
            endwhile;
        endif;
    </div>
</div>