Just FTP Evox to your Xbox, and run it. It doesn't need to be in ISO form, or XISO, you just need the evox.xbe file and a suitable evox.ini - the .ini with the standard Evox download will work. Or you can use Config Magic to backup the eeprom, again transferred to your Xbox via FTP.
If you softmod you need the eeprom as an insurance policy. If you chip your Xbox it is less essential, but still a good idea.