To edit a passage, you can either double-click it on the story map or select it, then choose Edit Passage from the Story menu. (You can open several passages for editing this way.)
The editor window has three main fields: the title of the passage, any tags that it has, and the body text. As you make changes here, the story map will update itself automatically. Close the window when you're done working.
The editor window's Passage menu contains a list of passages that the one you're editing link to (the Outgoing Links submenu), other passages that link to this one (Incoming Links), and links from this passage that don't have matching passages (Broken Links). Selecting a passage title from these menus will open it if it already exists, or create a new passage with the appropriate title if it doesn't.
To concentrate just on a passage's text, choose View Fullscreen from the Passage menu. In the fullscreen view, press the Escape key to close the passage and return to the story map, or press F12 to switch back to the windowed view.
A shortcut exists for adding links: Select the text you'd like to use for the link and then drag and drop the link text into the story map. This adds square brackets around the text you've selected, creates a new passage for the link to go to, and opens it for you for editing.
If one of your passages contains a broken link – that is, it has a link pointing outward that does not have a matching passage – then an exclamation point emblem will appear on the passage on your story map, to warn you that there is a problem.
To remove a link, just delete the double brackets around the text.