This documentation is for a development version of IPython. There may be significant differences from the latest stable release (1.2.1).
You need to do this only once. The instructions here are very similar to the instructions at http://help.github.com/forking/ - please see that page for more detail. We’re repeating some of it here just to give the specifics for the ipython project, and to suggest some default names.
You then need to configure your account to allow write access - see the Generating SSH keys help on github help.