Download and install Processing software

Processing is an open source programming language and environment for people who want to create images, animations, and interactions. Initially developed to serve as a software sketchbook and to teach fundamentals of computer programming within a visual context, Processing also has evolved into a tool for generating finished professional work. Today, there are tens of thousands of students, artists, designers, researchers, and hobbyists who use Processing for learning, prototyping, and production.

To download and install is very straightforward:

Visit http://processing.org/, select Download, download the Mac, Windows, or Linux version, depending on what machine you have.

Reference: Getting Started

Next:
- Setup Processing for Android development
- Hello World of Processing for Android