Your first site
What a site is, and where one is created.
A site is a platform's public face: pages you edit and publish, a navigation tree, redirects, and the sitemap and robots file that follow from them. Platforms and sites describes the pieces.
Sites are created and edited in the Console, which is not self-serve today, so this page does not yet carry a walkthrough.
What is available to read now is the API: every site operation — listing and creating pages, publishing a page, reading its revisions, editing navigation and redirects — is in the sites reference, including which scope each one requires.