Grab the latest release from the GitHub releases page. Or if you are feeling adventurous, clone the live source from the master branch.

Flash the core of Octoduino to your Arduino board. You MUST use PlatformIO, the Wiring Arduino IDE will NOT work. See the GitHub wiki for help.

Copy everything IN the ~/boot folder to a blank SD card that is less than 4GB big and formatted to FAT32.

Right now, there are no stable parsers available. See the instructions on the wiki to see how to get started writing your own.

Attach the Ethernet shield, stick the SD card in, then apply power. Make sure you have a serial window open (Please use the one provided by the Arduino IDE).