An easy way to get the post author meta data.
Place the code snippet below at the top of your page or component.
$author_id = $post->post_author;
$author_name = get_the_author_meta('display_name', $author_id);
$author_url = esc_url( get_author_posts_url($author_id));
Echo the required author data where needed.
<span class="author">by <a href="<?= $author_url; ?>"><?= $author_name ?></a></span>