Could you please expand on this a bit more? I think you are referring to the documentation at:
What are you trying to achieve? The documentation describes downloading the notebook as a whole (which gives you a .tgz file).
If you want to access your notebook through the API and embed it somewhere, you can call the API server and render the cells as described here. The code for that is also shown when you use the embed option on the notebook and look at the JavaScript embed option.