We don't have any templates that will allow you to save written essays or short answers (yet), but you can put a mult-line textbox into any basic screen that allows text.
If you go into the html editor of some text-content (denoted by '<>' at the bottom left of the editor), sample html for multi-line textbox is:
<textarea rows=5 cols=25></textarea>
Note that it won't show the text box with more than one line in the editor, but when you save it you'll have a multi-line textbox on the screen you are editing.