Show Previous/Next Article Link In Posts Without Plugin - https://www.techmuzz.com/how-to/wordpress/show-previousnext-article-link-in-posts-without-plugin/

functions.php

function techmuzz_navigation_links() {
    if ( is_singular('post') ) { ?>
        <div style="background: #eee; border: 1px solid #bbb;display:inline-block;padding:5px 10px 5px 10px;margin-bottom:10px;">
            <span class="nav-previous alignleft" style="width:45%;">
                <?php previous_post_link('<strong>%link</strong>', '<span style="color: #333;"><< Previous Post</span>', TRUE) ?><br/>
                <?php previous_post_link('%link', '%title', TRUE) ?>
            </span>
            <span class="nav-next alignright" style="width:45%;">
                <?php next_post_link('<strong>%link</strong>', '<span style="color: #333;">Next Post >></span>', TRUE) ?><br/>
                <?php next_post_link('%link', '%title', TRUE)?> 
            </span>
        </div>
    <?php
  }
}
add_action('genesis_entry_footer', 'techmuzz_navigation_links' );