How to add author bio in Author archive page?

Go to Appearance> Editor and Open up layout1.php and add this:

<?php if(is_author()){ ?>

<div class="author_div">
<?php
if(isset($_GET['author_name'])) :
$curauth = get_userdatabylogin($author_name);
else :
$curauth = get_userdata(intval($author));
endif;
?>
    <div class="author_left"><?php echo get_avatar($curauth->ID, $size = '100'); ?></div>
    <div class="author_right">
    <h2><?php echo $curauth->display_name; ?></h2>
    <?php echo $curauth->user_description; ?>
    </div>
</div>

<?php } ?>

after this:

<div class="lay1">

This will display the author name, avatar and bio.