How to Hide the "Launch My Batsignal" Admin Menu

function plt_hide_batsignal_menus() {
	//Hide the "Launch My Batsignal" menu.
	remove_menu_page('l0nch_my_batsignal-plugin');
}

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

Where do I put this code?