Installing WHMXtra is easy, just log in through SSH and run the following commands:

cd /home
wget http://whmxtra.com/pro/pro.sh
sh pro.sh

Then login to WHM, go to Plugins, select WHMXtra and continue with the installation.

Removing WHMXtra is also easy, log in through SSH and run the following commands:

cd /home
wget http://whmxtra.com/pro/remitall.sh
sh remitall.sh

When the command is completed, WHMXtra will be uninstalled.