The Getting started guide has most of the details you need in order to get started.

You'll find a more thorough reference in the client README file. Here, you'll find out how to integrate with your CI environment, get a list of all the configuration options and more.

Refer to the API docs if you want to write your own integration with the service. This is useful if you know how to take screenshots yourself, but want to leverage the diffs and review abilities of Happo.