• Sage Cells: Click inside the box to make Sage cells. Drag around Sage cells however you want.
• Text boxes: Shift-click to make text boxes. Double-click to edit text boxes; drag them to move them. Inside the text boxes, math inside dollar signs works. Also, you can use Markdown to mark up text, or just use HTML as part of Markdown.
• Frozen pages: to save your creation as a web page, click "Frozen page".

Frozen page