First off, you need the program Processing.
Download it here: https://processing.org/download/

After installing it, launch the program, and paste the code from processing-code.txt into it.
Save the file. The file will be inside the "Processing" directory where it was installed.

It will complain about not finding an image, so that's where you need dickbutt.
Copy dickbutt.jpg into your project folder. The project should be under "Processing" inside the folder 
with the name of your project.