[cinq]

Just insert code similar to this :

PHP Code:

<form action="search.php" method="post">
<input type="hidden" name="s" value="$session[sessionhash]">
<input type="text" class="bginput" name="query" size="18">
</form> 


somewhere within your html or php page where you want to have the search box.
You have to format it to fit it into your page though.
Hope this helps