To get started with Android/JellyBeer, you'll need to get familiar with Git and Repo.
To initialize your local repository using the CyanogenMod trees, use a command like this:
repo init -u git://github.com/BeerGang/android.git -b cm-10.1
Then to sync up:
repo sync
And to start building:
./jb-build.sh DEVICE_NAME
Or if you want to sync and build:
./jb-build.sh DEVICE_NAME true