I'm trying to remove the sub-menu drop down for the main menu at the top. I've read this here - http://codex.wordpress.org/Template_Tags/wp_list_pages#Notes
But I haven't used wordpress for quite sometime and don't exactly remember where to edit to adjust these codes.
The code in the header is currently as below
<nav id="access" role="navigation">
<h1 class="assistive-text section-heading"><?php _e( 'Main menu', 'toolbox' ); ?></h1>
<div class="skip-link screen-reader-text"><a href="#content" title="<?php esc_attr_e( 'Skip to content', 'toolbox' ); ?>"><?php _e( 'Skip to content', 'toolbox' ); ?></a></div>
<?php wp_nav_menu( array( 'theme_location' => 'primary' ) ); ?>
</nav><!-- #access -->
