You must install Lerna to build this multi-package repository.
$ npm install -g lerna
Once Lerna is installed, and this repository is cloned, then you must bootstrap the repository so that all of the dependencies are installed and all of the packages are linked together:
$ lerna bootstrap
You can then work with the packages under packages/ on a per-package basis as any normal node.js package.
Alternatively, you can execute npm commands across all of the packages at once using Lerna:
$ lerna run test