If your next question is about shaping the site, open the configuration guide. If the question is about what the authoring surface can do, go to Markdown writing features. Diagram-specific behavior lives in the Mermaid guide and the D2 guide, while shell styling and theme presets are covered in theming.
Use security when the site needs login or path rules, architecture when you want the request and rendering model, and advanced behavior when you are past the happy path and want the edges.
The manual itself starts at vyasa manual/README.md, but you should not need it before the quick start above works.