Author page assistance

I’m working on my localhost on a new layout for my website. I’m working from a theme called Instinct and I’m attempting to change the default Author Archive to a full Author Page complete with bio, information, links, posts, etc.

The theme requires that I create a new php called post-author.php, which I did. When this is made, the Author.php loop draws from this rather than the default post.php.

When I attempt to alter this new template, I get lots of trouble. For instance, I add this small bit of code (or any code for that matter) and when previewed, it duplicates itself over and over down the page.

<p class="listhead">You're in the <b>Author Archive</b></p>

    <!-- This sets the $curauth variable -->
    <?php
    if(isset($_GET['author_name'])) :
    $curauth = get_userdatabylogin($author_name);
    else :
    $curauth = get_userdata(intval($author));
    endif;
    ?>

I need help. I’m only learning and this task has become more cumbersome than originally anticipated.