If you want to add a search box to your template/theme, add the following to the appropriate file:
<?php echo $this->getChildHtml(‘topSearch’) ?>
For example if you wanted to add the search box to your header file, you’d add the above code to /app/design/frontend/default/your_theme/template/page/html/header.phtml. You can then modify your style.css file to style the search box.
It’s as simple as that!
also you will need to edit css and make it look pretty