Yes, the easiest way is to use the "source" button and add it directly to the HTML code.
Once you see the code, scroll all the way to the bottom of all the code and add this (but obviously put in your own footer content):
<p> Here's my footer content... </p>
So it will look like this:
Let me know if you get stuck or have other questions and I'd be happy to help you get this working!