Amend theme php to include certain category in header

I’m using a free theme on my WordPress site, and the index.php is the following:

<?php if (have_posts()) : ?>

    <?php
    $paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
    $total_post_count = wp_count_posts();
    $published_post_count = $total_post_count->publish;
    $total_pages = ceil( $published_post_count / $posts_per_page );

    if ( "1" < $paged ) : ?>

        <div class="page-title">

            <h4><?php printf( __('Page %s of %s', 'hitchcock'), $paged, $wp_query->max_num_pages ); ?></h4>

        </div> <!-- /page-title -->

        <div class="clear"></div>

    <?php endif; ?>

    <div class="posts" id="posts">


        <?php while (have_posts()) : the_post() ; ?>


            <?php get_template_part( 'content', get_post_format() ); ?>

        <?php endwhile; ?>

        <div class="clear"></div>

    </div> <!-- /posts -->

<?php endif; ?>

<div class="clear"></div>

<?php hitchcock_archive_navigation(); ?>

This shows the latest posts on my website. I want to amend this code to only show posts from a certain category instead. Is this something that I can just amend or add code?