You need to study Chapter 15. Data Exchange Mechanisms of the Developer Guide
In a few words you need to understand XML documents read and write tools XML-serialization Exchange plans
Also you might want to have a look at LoadDataXML82.epf data processor in ext directory which comes with Hello 1C master class: This data processor allows to import XML data and also conatins Unloading form item group which is invisible by default (to make it simpler due to it's a master class) for data export.