Newbie trying to develop & debug for OpenHab

For homeconnect I am trying use the OSGI Bundle found at the link below. How to download it etc how to work with it ? followed his guide

Rather than what i did right now: just directly work with the JAR file and UI which I downloaded from here:
Home Connect addon: Looking for beta testers.

I pasted this in addon and included this binding. and it works but I have no code access etc.

I tried sending commands through Karaf console but where do I develop a script in which I can make my own program . Like instead of JAR files how do u deal with bindings to customize them in code rather than UI?

Regards,
Owais Ahmed.