How to show secondary menu to looged in users only

Hi, I have a quick question on primary/ secondary menu in wordpress. I have just enable the secondary menu in functions.php and now I would like the secondary menu to only show for logged in users and primary to all.
I know I have to change the header.php file a bit, but I am not sure how – here is the excerpt of my header.php with the respective menu codes:

<div id="top-navigation">
				<nav>
				<?php
					$menuClass = 'nav';
					if ( 'on' == et_get_option( 'explorable_disable_toptier' ) ) $menuClass .= ' et_disable_top_tier';
					$primaryNav = '';
					if ( function_exists( 'wp_nav_menu' ) ) {
						$primaryNav = wp_nav_menu( array( 'theme_location' => 'primary-menu', 'container' => '', 'fallback_cb' => '', 'menu_class' => $menuClass, 'echo' => false ) );
					}
					if ( '' == $primaryNav ) { ?>
					<ul class="<?php echo esc_attr( $menuClass ); ?>">
						<?php if ( 'on' == et_get_option( 'explorable_home_link' ) ) { ?>
							<li <?php if ( is_home() ) echo( 'class="current_page_item"' ); ?>><a href="<?php echo esc_url( home_url( '/' ) ); ?>"><?php esc_html_e( 'Home','Explorable' ); ?></a></li>
						<?php }; ?>

						<?php show_page_menu( $menuClass, false, false ); ?>
						<?php show_categories_menu( $menuClass, false ); ?>
					</ul>
					<?php }
					else echo( $primaryNav );
				?>
				</nav>
				<div class="et-search-form">
					<form method="get" class="searchform" action="<?php echo esc_url( home_url( '/' ) ); ?>">
						<input type="text" value="<?php esc_html_e( 'Search this site...', 'Explorable' ); ?>" name="s" class="search_input" />
						<input type="image" src="<?php echo $template_directory_uri; ?>/images/search-icon.png" class="search_submit" />
					</form>
				</div> <!-- .et-search-form -->
			</div> <!-- #top-navigation -->

Appreciate if someone can quickly help.

Cheers,
Dirk