Adding a Footer with Excerpts

Trying to create a homepage that displays the most recent post with a large featured image, and then three horizontal thumbnails of three other recent posts beneath it in the footer with their summaries.

So, it will look something like:

----------------HEADER-------------------

 *Most recent post title*   ----SIDEBAR---
-----------------------     |            |
|                      |    |            |
|     Featured         |    |            |
|     Image            |    |            |
|                      |    |            |
------------------------    |            |
Summary of recent post,     |            |
lorem ipsum... READ MORE    |            |
                            --------------
  *Title*         *Title*       *Title*
----------      ----------     ----------
|  img   |      |  img   |     |  img   |
----------      ----------     ----------

The rest of it I’m okay with, but the footer, I have no idea where to start. I have a footer.php in my child that I copied from the parent, but am not sure where to start editing it.

Thanks in advance.