Customizing configuration data?

I'm trying to cusomize the configuration data in a project area. The
example for retrieving the data on the client does not explain how to
get the IProcessArea, and does not explain how to get the repository in
order to call getClientLibrary():

IProcessArea processArea = findProcessArea(parameter);
IProcessClientService processService = (IProcessClientService)
repository.getClientLibrary(IProcessClientService.class);

Where can I find the documentation that can fill in the missing pieces?

Bryan