Until 10 minutes before the start of this month I had a VPS at Digital Ocean running with Jenkins and Gitolite on it for privately hosted repositories. With Github's recent move to unlimited repositories I really didn't have a need to host them myself anymore, and after playing with CircleCI's free tier it didn't make any sense anymore to keep that VPS up.
He starts by outlining some of the prerequisites to get in place before trying to set up the process on your own application. He shows you how to set up an IAM user for the S3 bucket and configure CircleCI though a simple YAML file. He also mentions the set up for tests, loading in other dependencies needed (Composer) and finally the deployment that executes Sculpin's "generate" command to build the site.