How to Hide the "ChatNow Live Chat" Admin Menu

function plt_hide_mychatnow_menus() {
	//Hide the "Settings → ChatNow Live Chat" menu.
	remove_submenu_page('options-general.php', 'options-chatra');
}

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

Where do I put this code?