How do I register a submenu?

first of all i don’t see the need for this piece of code? unless you are inserting content with css or javascript?

else
?>
<ul id="current">
<?php if (is_page('About')) {
echo " id=\"current\"";
}?>
</ul>

second please review the codex docs about the wp_nav_menu: https://codex.www.ads-software.com/Function_Reference/wp_nav_menu

Your nav function should look something like this:

<?php 

if(function_exists('wp_nav_menu')) {

    wp_nav_menu( array(
            'theme_location' => 'primary_nav', //Use theme location as that is the menu location you registered it against
            'container'      => '', // Seeing as you already include the function in a container this is fine
            'depth'          => 0 //Include all menu items of any depth
        )
    );

}

?>

Thank you so much for your reply.

The piece of code in question is the only way I could make the current page in the nav bar be highlighted (the green spiky behind the text). If you have a cleaner way, I’m open to suggestions! I had tried about 2 different things before I found one that worked.

Update — I just realized I had .current_page_item already coded to have the green spiky image behind the text, which I found thanks to the link you provided. I’ve deleted that piece of code in question entirely. Thanks for that!

Unfortunately my menu is still not working (dev.adambobrow.com). As you can see, the child items of “About” are showing up. This happened after I changed ‘depth’ to 0.

How do I hide the two items under “About” and only have them show up upon mouse hover?

Based on the link provided in the above response, I added some code to functions.php where my menu is, starting with “add_filter”:

/* MENU */
add_theme_support( 'menus' );

if(function_exists('register_nav_menu')):
	register_nav_menu( 'primary_nav', 'Primary Navigation');
	register_nav_menu( 'videos_nav', 'Video Categories');
endif;

add_filter( 'wp_nav_menu_objects', 'add_menu_parent_class' );
function add_menu_parent_class( $items ) {

	$parents = array();
	foreach ( $items as $item ) {
		if ( $item->menu_item_parent && $item->menu_item_parent > 0 ) {
			$parents[] = $item->menu_item_parent;
		}
	}

	foreach ( $items as $item ) {
		if ( in_array( $item->ID, $parents ) ) {
			$item->classes[] = 'menu-parent-item';
		}
	}

	return $items;
}

Here is my nav markup:

<div id="nav">
            <div id="navmenu">

                	<?php if(function_exists('wp_nav_menu'))
						wp_nav_menu(
									array(
										  'theme_location' =>'primary_nav',
										  'container'=>'',
										  'depth'=>0,
										  'menu_id'=>'menu',
										  'dropdown_class'=>'dropdown',)
						);
						else
					?>
            </div>
            </div>

I can see through the “inspect element” feature on Chrome that I now have a ul class called “sub-menu.” I am just not sure what to do with it. Playing with the display properties yielded no satisfactory results. I think I just need a little more help to get this to work.

Thank you!

Never mind, I got it — I put

#nav ul li:hover > ul {
	display: block;
}

and it works. Just need to style the rest. Thank you!

marking this as resolved.