How to develop report using IReport / JasperReport connected to MongoDB

Hi all,
we have to develop some custom report using IReport / JasperReport.
The connection to db works but it’s not easy to understand how to make queries and find right data using MondoDb collections and documents.
Someone of the group has, in past, developed some specific reports using these applications ?
Are you so kind to explain in easy words how to treat data using a no sql db ?
We are used to query for istance master/details in classic SQL db and it’s not clear how retrieve correct data using MongoDb.
I’m a functional consultant and I got difficult to explain better concepts.
Maybe a couple of samples can help us to understand how to do it.
Thanks very much