You will now see an additional row of links in a bar above the page content: contents, view, edit, properties and sharing. You need only concern yourself with the view and edit functions for now.

Click edit to go to a screen that lets you edit the document.

Here you can edit the contents of the document. You will see that the part of the document that goes in the description box gets presented to the user in bold text with the contents of the Body text displayed below in normal font.

Make your changes and save the document