Candlepin documentation is split into three major pieces. A Jekyll based web site https://candlepinproject.org/, JavaDoc that is currently only in the source code and REST API that is being hosted on https://candlepinproject.org/ and is auto-generated by OpenAPI from our API spec.
When you need to submit new documentation, you should clone sources of the site from Github repo and issue a Pull Request. After your pull request is merged, the new site content is automatically published to https://candlepin.github.io/
While preparing the Pull Request with changes to the documentation you should use local Jekyll instance to see your changes to the documentation. See README.md file in site’s sources.