Before you start playing with/hacking on the Telepathy integration stuff, you need to have the latest version compiling and working: Instructions
The best way to get involved is to start on some "junior jobs". These are small bugs or features that exist in our applications that are a good way to get to learn the code, and learn our workflow process
A list of junior jobs can be found here.
If you want to work on any of those, get in touch!
If you want to work on a feature, clone the git repository on the server side and then clone your personal clone on your local machine. Make a new git branch and start working there. Try to keep commits small and meaningful. Once you are finished, push the branch on your server-side clone and ask someone of the team to review it. Once it is reviewed, you can merge it on the master repository (or ask someone else to merge it).