This repo uses Jekyll to serve pages, which can be installed here.
Once installed just run the command jekyll serve in your terminal in the root directory of this repo. In the output in your console from this command you will see Server address: <base_url>, visit this base_url in your browser and you will see the content on fabricjs.com with your local changes applied.
Best place to start is by going through 4-part tutorial
Here's a hierarchy of Fabric's object model, to make it easier: