Manual Link Among Page Listing Menu

Existing code in header.php:

<?php if (is_page()) { $highlight = ""; } else {$highlight = "current"; } ?>

<div id="mainmenu">
<ul class="level1">

<li class="<?php echo $highlight; ?>"><a href="<?php echo get_settings('home'); ?>"><?php _e('Home','andreas09'); ?></a></li>
<?php
if(function_exists("wp_andreas09_nav")) {
wp_andreas09_nav("sort_column=menu_order&list_tag=0&show_all_parents=1&show_root=1");
}
?>

</div>

How do I code (and where to put) a manual link to be appear in the menu bar?

Thanks!!