How to enable commenting system in WordPress

I am learning how to create custom WordPress theme from this page
and everything is working except commenting system because they haven’t described how to enable it (they only used <?php comment_form(); ?> to insert form into template). I can see my comment in the backend but not in the page itself (I can see a link showing 1 comment but when I click it nothing happens). Obviously I need some PHP code to show my comments but have no idea where to start! I am stuck because I just started to learn Theme Development and my PHP knowledge is limited.
Can anyone give me a suggestion or a solution for that problem? It would a mean a lot to me.
Index php looks like this:

<?php get_header(); ?>

<div id="blog">
    <?php if(have_posts()) : ?><?php while(have_posts()) : the_post(); ?>

    <div class="post">
    <h3><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h3>

        <div class="entry"> 
            <?php the_post_thumbnail(); ?>
            <?php the_content(); ?>

            <p class="postmetadata">
            <?php _e('Filed under:'); ?> <?php the_category(', ') ?> <?php _e('by'); ?> <?php  the_author(); ?><br />
            <?php comments_popup_link('No Comments »', '1 Comment »', '% Comments »'); ?> <?php edit_post_link('Edit', ' | ', ''); ?>
            </p>

        </div>
    </div>

    <?php endwhile; ?>

    <div class="navigation">
    <?php posts_nav_link(); ?>
    </div>

    <?php endif; ?>
</div>

My WordPress page HERE
Thank You!!