In order to upgrade your PHP-Nuke, please follow the instructions described in its documentation at:

http://phpnuke.org/modules.php?name=PHP-Nuke_HOWTO&page=upgrade-php-nuke.html

However, since this process is quite complicated and could cause great damage to your website, we advise our customers to take advantage of our Exclusive Professional Services. You only have to post a ticket with your request in your Helpdesk section->Exclusive Professional Services->Application upgrade.