That's it. Pretty simple. There's also a drop-down option in the upper right to switch between various views:
- Preview: A live display of the generated HTML as it would render in a browser.
- HTML Source: The generated HTML before your browser makes it pretty.
- Lexer Data: What [marked] uses internally, in case you like gory stuff like this.
- Quick Reference: A brief run-down of how to format things using markdown.