CyberGhost Immunizer tricks the Petya ransomware into thinking that your computer is infected causing it to move on.
Installation is all there is to it. Simply double-click PetyaImmunizer.exe and a message will appear that it installed correctly as seen in the screenshot below.
The app is portable so it can be deleted after the first run, however uninstalling is not so easy. You'll need to go the Windows directory and delete perfc, perfc.dll & perfc.dat. If you're not familiar or comfortable deleting files then this isn't for you.
The Petya ransomware spread like wildfire and CyberGhost Immunizer is one way to set-it-and-forget-it on a customer's computer who you consider vulnerable.