How to Hide Landingi Landing pages Admin Menus

function plt_hide_landingi_landing_pages_menus() {
	//Hide "Landingi".
	remove_menu_page('landingi');
	//Hide "Landingi → Available Landings".
	remove_submenu_page('landingi', 'landingi');
	//Hide "Landingi → Imported Landings".
	remove_submenu_page('landingi', 'edit.php?post_type=landing');
	//Hide "Landingi → Settings".
	remove_submenu_page('landingi', 'landingi_settings');
}

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

Where do I put this code?