Before starting the installation make sure ionCube Loaders are enabled.
Please make sure that the Ioncube loader is selected for the backend copy of PHP
Login to WHM (root)
Go to Server Configuration -> Tweak Settings -> PHP
Select ioncube from the radio-button for cPanel PHP loader.
Click on Save button.
That's it. This will enable Ioncube for you in 3rd party PHP binary
Now SSH to your server and enter following commands :
wget -N http://files.softaculous.com/install.sh
chmod 755 install.sh
Now go to : WHM > Plugins (Add-Ons on older versions than 11)
> Softaculous - Instant Installs