Hold down the Alt key and click here -->
Now type something.
As you can see, the item has become editable. To turn editing back off, simply Alt+click in the item's body again. The item body supports bold, italic, underlined, superscript and subscript text, as well as headers, horizontal rules, and links – basically, anything you can do in HTML/CSS is available to you, one way or another. Formatting commands are issued via key combinations, but don't worry about memorizing them all. The PROTODOCUPLEXTRON makes use of command palettes, which you shall become acquainted with presently.
Let's first introduce the Selection Ops palette. If this item isn't already editable, make it so by Alt+clicking on it. Next, invoke the Selection Ops palette by pressing Alt+C. You should see it now in the upper-right corner of the screen. When the command palette is visible, it means the PROTODOCUPLEXTRON is awaiting a keypress to perform a command. If you decide you don't want to issue a command, you can dismiss the palette by pressing the escape key or clicking away from it.
To see how this works, select some text in this item and press Alt+C to invoke the Selection Ops palette. Next, press the B key to embolden the text you've selected. You can undo this by pressing the usual system undo command, Ctrl+Z. Alternatively, you could select the text again, press Alt+C to activate the Selection Ops palette, and press F to strip all the formatting from your selection.
The sky is really the limit with what you can do inside an item, and you can certainly jump ahead to the Advanced Editing section if you like, but it might interest you first to learn how to Dismiss, Delete, and Create items.