An ISO image is a bit copy of a CD. You can burn this image to a blank CD and boot from it.

To burn an ISO to a CD you need an ISO burning program. The simplest program for this is ISO Recorder http://alexfeinman.com/isorecorder.htm

You can follow the instructions here.

http://pcsupport.about.com/od/toolsofthetrade/ht/burnisofile.htm

If you have a MAC you can use Disk Utility

http://hints.macworld.com/article.php?story=20060619181010389

Next set the BIOS on the target machine to have the CD/DVD drive be first in the boot order, before the internal hard drive. See http://www.hiren.info/pages/bios-boot-cdrom and http://pcsupport.about.com/od/fixtheproblem/ss/bootorderchange.htm On some computers you can press F10 or F12 during boot and select the boot device.

Once the CD is booted you can select the image to install.

WARNING: Installing an image will erase all data on the target computer

Once your image is installed you will be prompted to reboot power off etc. Select reboot.

Remove the CD from the drive so it won't boot again.

Your image is installed!