cd your public_html/ and create OLD_WP/ folder
mkdir OLD_WP/
This will move WordPress' files/folders into the OLD_WP/ folder
mv wp-* index.php .htaccess robots.txt *.sql license.txt readme.html sitemap.xml xmlrpc.php error_log cgi-bin -t OLD_WP/
Then move it to level up
mv OLD_WP/ ../