Many thanks Dude!!
For others reading, using the WP control panel I selected “Appearance”, then “Editor”. At the bottom of right hand column, I loaded up style.css file which is the main stylesheet defining fonts, backgrounds, text size, etc.
I then created the following line per Dude’s instruction, and clicked on “Update File”:
Poof, it appeared. Note: I had already edited the bg.png file to a background I wanted in the header, and uploaded it to the url above. So now both header and footer match.