You can get started online or by working locally with your downloaded version of NuPyCEE.
For the download and installation of necessary python modules see Installation. How to work with the NuPyCEE modules is shown via ipython notebooks for SYGMA here, for OMEGA here and for STELLAB here. The usage of the notebooks with your NuPyCEE copy is explained in the GettingStarted directory of NuPyCEE. Alternative to ipython notebooks you can use the ipython commands in your interactive ipython session inside the NuPyCEE root directory as shown below.
For more in-depth explanations see the Modules tab in the top bar.
Teaching material worth for beginners is available in Teaching.
For details of the code and in particular plotting functions see the Documentation.
Don't hesitate to look into the source code which contains various comments.