For a deeper look into our Eikon Data API, look into:
Overview | Quickstart | Documentation | Downloads | Tutorials | Articles
Please check out this tutorial, which talks at length about metadata discovery (finding field names and parameters) for use with Eikon Data APIs. Instead of Data Item Browser app described in the tutorial, you can use CodeCreator app, which is very similar, except that as output it produces code snippets, which you can copy & paste into your code.