Please first visit:
Main >> Server Configuration >> Tweak Settings >> PHP
Set the cPanel PHP loader to IonCube!
Once its licensed, login thru SSH, and do the following:
wget -N http://files.softaculous.com/install.sh chmod 755 install.sh ./install.sh
This will install & register the plugin.
Now go to:
WHM > Plugins (Add-Ons on older versions than 11) > Softaculous - Instant Installs
The following webpage will open if the installation was successful.