if you have a WordPress site and have search engines finding <yoursite>/author/admin or <yoursite>/author/a<name of author> and you don’t want this without adding another plugin (like Yoast SEO) then the following steps will redirect this page to your homepage

In WordPress admin console, navigate to Appearance > Theme File Editor.  Once there, select functions.php from the right hand side.

Using the editor, add the following as a new line at the end of the file –

function my_custom_disable_author_page() {
  global $wp_query;

  if ( is_author() ) {
      // Redirect to homepage, set status to 301 permenant redirect. 
      // Function defaults to 302 temporary redirect. 
      wp_redirect(get_option('home'), 301); 
      exit; 
  }
}

Save the file and now your site wont publish such pages.