How to call in only one category of blog posts via the loop

I am working in a template and want to display only the latest article of one category of posts on the home page and display the full post? I am not clear on how to modify this loop. Any suggestions?

<div class="message_center_left">

<?php
if ( function_exists( 'get_option_tree' ) ) {
$featured_number = get_option_tree( 'vn_selectnumberblog' );
} ?>

<?php
$featured = new WP_Query('&showposts=' . $featured_number);

while ($featured->have_posts()) : $featured->the_post();
?>

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

<hr />

<?php endwhile; ?>

<?php wp_reset_query(); ?>

<?php
if ( function_exists( 'get_option_tree' ) ) {
$morenewstext = get_option_tree( 'vn_morenewstext' );
$morenewslink = get_option_tree( 'vn_morenewslink' );
} ?>

<?php if ($morenewstext != ('')){ ?>
<a>"><?php echo stripslashes($morenewstext); ?></a>
<?php } else { } ?>

</div>

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