Replicating content in custom template

Hi guys, I’m just dipping my toe into templates and I probably need a little help. Basically I’m using twenty twelve and I needed a different template for some pages. So in my child theme I created a new template file, which is now successfully showing up in the template menu when I create a new page. It’s very basic for now, as you can see:

<?php /* Template Name: New Test page*/ ?>
<?php get_header(); ?>
<?php get_footer(); ?>

I want the user to be able to insert as many
<div class="portfolioBox"></div>
as they want in the page without modifying the HTML though. What would be the best way to achieve that? Would this be classified as a repeater?
Any advice is welcome as usual
thanks