How to Hide WP Retina 2x Admin Menus

function plt_hide_wp_retina_2x_menus() {
	//Hide "Media → Retina".
	remove_submenu_page('upload.php', 'wp-retina-2x');

	//Hide "Meow Apps".
	remove_menu_page('meowapps-main-menu');
	//Hide "Meow Apps → Dashboard".
	remove_submenu_page('meowapps-main-menu', 'meowapps-main-menu');
	//Hide "Meow Apps → Retina".
	remove_submenu_page('meowapps-main-menu', 'wr2x_settings-menu');
}

add_action('admin_menu', 'plt_hide_wp_retina_2x_menus', 11);

Where do I put this code?