What do I do with this error on installation?

Fatal error: require(): Failed opening required '/homepages/24/d405765077/htdocs/HagarFinal/libraries/ClassLoader.php' (include_path='.:/usr/lib/php5.5') in /homepages/24/d405765077/htdocs/HagarFinal/libraries/composer_autoload.php on line 22