How to Hide the "Twitter Feed Auth" Admin Menu

function plt_hide_oauth_twitter_feed_for_developers_menus() {
	//Hide the "Settings → Twitter Feed Auth" menu.
	remove_submenu_page('options-general.php', 'tdf_settings');
}

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

Where do I put this code?