To get started with this, you'll need to get familiar with Git and Repo.
To initialize your local repository using the sg3 trees, use a command like this:
repo init -u git://github.com/sg3/apollo_manifest.git
Then to sync up:
repo sync
After you're done with syncing, type
./build.sh build
For building.
All the supported commands can be viewed by typing
./build.sh help