This is editable text. You can focus it and start typing.
To apply styling, you can select a piece of text and manipulate its
styling from the menu. The basic schema supports emphasis,
Block-level structure can be manipulated with key bindings (try ctrl-shift-2 to create a level 2 heading, or enter in an empty textblock to exit the parent block), or through the menu.
Try using the “list” item in the menu to wrap this paragraph in a numbered list.