Go to the pfSense download mirror page
Select a nearby mirror and download the latest appropriate image. For this hardware and a 4GiB CF card, it will be:
Write the image to the CF card with the command:
zcat pfSense-<VERSION>-RELEASE-4g-i386-nanobsd.img.gz | sudo dd of=/dev/path/to/cfcard bs=64K
^^^ the above renders fine on desktop, but on mobile the
1. is floating off to the right.