Author name needed to appear with each post but not doing it

Ok I am really new at this but would like my posts to have the authors name listed below their posts and right now they do not show up.

Just installed WP a week ago 1-10-07.

With this in mind, I have read it needs to go in the “loop”, wich I assume is index.php but not understanding, when I open this file, where exactly do I insert the following

<?php
global $wp_query;
$author = $wp_query->get_queried_object();
echo $author->user_firstname . ‘ ‘ . $author->user_lastname;
?>

If someone could paste in exactly the code that I should see in this index.php file that would come right before the ABOVE code is inserted, and also paste the code I should see that would be showing right AFTER it, I’d sure appreciate it.

Also is the above code correct for the version I have installed if its only been a week ago?

Just want to make sure I am doing this right.

Anything else I have to do to enable / allow it to display or will this take care of it?