How to get black border around entire homepage?

Hello, everyone, another newbie question! I would like to have a thin black border around my entire homepage. I am able to get the border around all of the other pages, but not the homepage.

My parent theme is twentyeleven and I do have a child .css file.

I’ve done multiple web searches on “get a black border around home page in WordPress” and tried pasting in pieces of code that seemed to make it work for others, when they asked similar questions, but so far I have not been successful.

The main problem, of course, is that I know nearly nothing about code and feel like I have the IQ of mayonnaise when I ask questions. I hope this is an easy fix, and thanks so much in advance for your replies.

Website = jvalenciaphoto.com