As stated on the Jupyter Project site:
The Jupyter Notebook is a web application that allows you to create and share documents that contain live code, equations, visualizations and explanatory text. Uses include: data cleaning and transformation, numerical simulation, statistical modeling, machine learning and much more.
Before you continue you should download and install the Jupyter Notebook.
However, if you just want to play along with the exmples go to the nbviewer, and enter the url to one of the notebooks (they will have the .ipynb extension): e.g.: 1. A Brief Introduction to Python.ipynb (if you just want to copy/paste the link: https://github.com/musicus/mango-chicken-fish/blob/master/1.%20A%20Brief%20Introduction%20to%20Python.ipynb).