Installing PC-BSD is very easy. However, you should review this section to make sure your hardware is supported and you know how to prepare your installation media.
Writing the ISO to Flash media
To write the USB IMG file to a Flash Card or USB pen drive you can do this with the Unix/Linux command dd:
dd if=<path_to/img_file.img> of=/dev/da0 bs=1m
Just substitute da0 with the device name of your USB stick.
NOTE: The USB images are FreeBSD-UFS formatted, and will not show up as a viewable file-system under Windows.
ADD SECTION ON how-to to flash a USB pen drive with the installer image. On Unix system this can be done with dd(1) and on Windows there's a nice tool with gui written by the M0n0wall crew: http://m0n0.ch/wall/physdiskwrite.php