Once you've signed up with your Github user, you'll see a list of your public repos. To [de]activate credo for a repo, just click on its On/Off button.
When a repo is activated, a webhook will be added to that particular repository on Github. Then, each time somebody submits a pull request there, CredoCI will check the PR's code with credo and report all warnings as github comments.
When CredoCI runs credo on your pull request it checks if there's a .credo.config file in your pull request's branch,
containing a config with name 'default'.
If there is one then it will use it. Otherwise, the default credo config is used. You can find more info on the format of the .credo.config file on credo repository.