Thanks Clyde,

Not sure how to go about it though. Do I need to edit any other files? For example if I want to creat an About Us page.
This is what I have done so far:
in includes/templates/mytemplate/common/tpl_header.php I have added this in

<li<?php echo (($current_page_base == 'about_us') ? ' class="current">' : ' >');?><a href="<?php echo zen_href_link( FILENAME_ABOUT_US, '', 'NONSSL'); ?>"><?php echo '<span>' . HEADER_TITLE_ABOUT_US . '</span>'; ?></a></li>

I have also changed the /includes/languages/english/html_includes/define_page_2.php to be

/includes/languages/english/html_includes/define_about_us.php

What else do I need to change as on my site the link says HEADER_TITLE_ABOUT_US and when pressed page is not found

THanks