You can install PHP-Nuke through the automatic script installation system - Softaculous following these steps:

1. Log in cPanel and go to Softaculous;

2. From Portals/CMS > PHP-Nuke click the "Install" tab and fill in the needed details;

You can also install PHP-Nuke manually. For this purpose follow these instructions:

https://www.siteground.com/tutorials/phpnuke/phpnuke-manual-installation.htm