There are a bunch of API Quickstarts available, and there's one that covers working with the repository.
This is the complete programming with ES4 site:
Adobe LiveCycle * Programming with Adobe LiveCycle ES4
And you can find the quickstart I'm talking about here:
Adobe LiveCycle * Repository Service API Quick Starts
Check the /sdk directory where LiveCycle/AEM is installed for the JARs you need to import into your applications.