If you have already downloaded the FULL-DISKfighter Mac DMG file (if not, go here to get it:
http://www.spamfighter.com/FULL-DISKfighter/Functions/Download-Mac.asp),
then find the DMG file, double-click it, and it will mount on your system, now drag FULL-DISKfigher Mac from the DMG file to your Applications folder.
It is now installed on your system.