Getting setup is easy, you'll need to have node.js installed, then simply clone the repository and within the working directory run the following:
# You only need to run this the first time
sudo npm install -g yarn
yarn install
# Run this to start the development server and build system
npm run dev
If you're on linux, you can simply type make and it will do all this for you as well.
Once running, you can then navigate to http://dev.beta.online-go.com:8080/ which loads the interface from your local server that you just started with gulp, and connects to the beta server for testing.