Full Width Header twentyeleven child

Hi, I’m a self-teaching-novice, learning by doing and trying to make the header & footer on my twenty-eleven child theme extend to full page width. I was able to find a simple fix for the footer here: https://springpadit.com/springpad/index.html#notebooks/websitewebstore/blocks/temp/new-Note?sort=created&view=detail&start=edit but I could not find a similar fix for the header. I know there must be some simple way I can alter my header.php but I don’t know what it is.

If anyone knows, I would appreciate the help on this. I’m doing really well otherwise and loving the theme, just stuck on this one issue!

Here is my site, showing the footer extending full width and the header not. https://www.heatherwatts.ca/

Thanks to anyone who can assist! ??