Hi Clara
By default the search field is built in to the template and is controlled from within the templates parameters. To convert this field to a module position try replacing the following in your templates header.php (../templates/j51_nocturne/php/layouts/header.php)..
<?php if($search_onoff == "1") : ?>
<div id="search">
<?php echo $search; ?>
</div>
<?php endif; ?>
With..
<div id="search">
<jdoc:include type="modules" name="search" />
</div>
Ciarán