Exibir Paginas e Categorias no Menu

Preciso exibir páginas e categorias no menu, o thema que estou usando esta exibindo os menu com esse código:


<?php

/*-----------------------------------------------------------------------------------*/
/* Register custom menu(s) */
/*-----------------------------------------------------------------------------------*/

function register_custom_menus() {
register_nav_menus(
array(
'main-menu' => 'Top Navigation'
)
);
}
add_action( 'init', 'register_custom_menus' );

/*-----------------------------------------------------------------------------------*/
/* Get custom menu // wp_nav_menu */
/*-----------------------------------------------------------------------------------*/

function get_custom_menu() {
if(function_exists('wp_nav_menu')) {
$lp_showMenu = wp_nav_menu(array('theme_location' => 'main-menu', 'menu' => 'main-menu', 'container' => '', 'depth' => '2'));
}
else {
$lp_showMenu = '

'.wp_list_pages('title_li&depth=2').'

' ;
}
echo $lp_showMenu;
}