how to display author name in custom post type

What I did wrong is, I forget to get author box, hence the_author function was not working, so I add this code in functions.php file

    add_post_type_support( 'my_post_type', array(
    'author', 'excerpt',
    ) );

then I got author box and in author box, set author name and add this code in custom post file

   the_author();

or

    echo get_the_author_meta('display_name');