Confused with highlighting a Primary Post

The CMS Questions
1

So i figured out the whole blog post in most recent order thing (the tutorial was great) But I’m having trouble understanding or finding how I can make the latest post a featured post with different styling and have a grid of posts underneath it. Basically want somthing like this:

<header>...</header>
<primary>post 4</primary> <-- make this big and prominent -->
<additional>post 3</additional>  <--grid of posts-->
<additional>post 2</additional>  
<additional>post 1</additional>  <--grid of posts-->
<footer>...</footer>
2 
<?php
$articles = $pages->find('blog')->visible();
$first = $articles->first();
?>

<primary>
 <h1><?php echo $first->title() ?></h1>
</primary>

<?php foreach ($articles->not($first) as $article): ?>
  <additional><?php echo $article->title() ?></additional>
<?php endforeach ?>

You also might want to read this about semantic HTML tags. Best practices but the above will work