When you create a redaction, it appears with a green underscore and the action buttons are shown:

Action buttons on a redaction.
The edit button gives you access to the edit popup window.
The blue button lets you propose the page for publication by an editor.
The wand button publishes the node (only appears if you have publication rights)
The wrench button gives you access to the drive popup.
To start writing text, you have to open the edit popup by clicking on the edit button. This small window contains two important tabs:

Tabs of the edit popup window.
The ‘text’ tab lets you write the main text for the page. The ‘title & Co’ lets you change the summary and the title.
To change the text of the page, simply start writing in the text area. Do not forget to click on ‘save’ or ‘validate’ to save your content. It is not because your text appears on the page that it is saved !
To insert links, images and produce advance formatting with title, sub-titles, lists and so on, please read about zazen.