Answer:

This is a mod, so do it at your own risk. You will need to keep a reference of this post or backup your files and apply this mod again if we update these files.

Go to Appearance > Editor and click on fetch-portfolio.php.

At the top is the image scaling argument:

$args  = array('postid' => $post->ID, 'width' => 680, 'height' => '', 'hide_href' => true, 'exclude_video' => false, 'imglink' => true, 'imgnocontainer' => true, 'resizer' => '680');

Change 680 to 940:

$args  = array('postid' => $post->ID, 'width' => 940, 'height' => '', 'hide_href' => true, 'exclude_video' => false, 'imglink' => true, 'imgnocontainer' => true, 'resizer' => '940');

Right below that is this code:

<li id="portfolio-content">       
    <h4><a href="<?php echo $link; ?>"><?php the_title(); ?></a></h4>
    <div>
        <?php the_content(""); ?>
    </div>
</li>

Highlight it and cut it (Ctrl+X)

Scroll down until you see this code:

</li>
        <?php endforeach; ?>
    </ul>          
     <ul class="next-prev-post-nav">
        <li>
            <?php if (get_adjacent_post(f

Place your cursor after <?php endforeach; ?> and hit Enter to create a blank line, then paste the code you cut into the blank line. You should now have:

</li>
    <?php endforeach; ?>
<li id="portfolio-content">       
    <h4><a href="<?php echo $link; ?>"><?php the_title(); ?></a></h4>
    <div>
        <?php the_content(""); ?>
    </div>
</li>
</ul>
 <ul class="next-prev-post-nav">
        <li>

Click Update File, then go to Theme Options and add the following to the Custom CSS:

.portfolio #portfolio-content {float: none; width: 100%;}
.portfolio #portfolio-image {float: none; width: 100%;}

Click Save Changes