How to change main query to only query posts from a single category? [duplicate]

<?php
    $catquery = new WP_Query( array( 'post_type' => 'post', 'category_name'=>'hello','posts_per_page' => 5 ) );
    while($catquery->have_posts()) : $catquery->the_post();
?>
<ul>
    <li>
        <h3>
        <a href="https://wordpress.stackexchange.com/questions/295915/<?php the_permalink() ?>" rel="bookmark"><?php the_title(); ?></a>
    </h3>
</li>
<li>
    <?php the_content(); ?>
</li>