Newbie, my menu changed when I inserted header in 2012 theme.

You’re gonna have to create a Child Theme for this change.

Thank you.
As a Newbie, do you mind if I ask you what a child theme does? What is it good for? Is it simpler?
And do I still need to make that change if I have the CSS style sheet editor that only overrides part of the original CSS?

Sorry, I’ve never done this before, and the instructions for the child theme seem a lot more complicated to me right now than they probably are.
Thanks

A WordPress child theme is a theme that inherits the functionality of another theme, called the parent theme, and allows you to modify, or add to, the functionality of that parent theme.

And do I still need to make that change if I have the CSS style sheet editor that only overrides part of the original CSS?

The change doesn’t require CSS.

Ok, thank you very much.
I followed the steps and my site looks like this now:
themindstyleblog.com
As you can see the Menu or “HOME” is still above the header. How can I change that now?

Copy header.php into your Child Theme directory.

Then in your Child Theme header.php file, replace all of the code with this; https://pastebin.com/QvJfyw1X .

Sorry for my utter stupidity, but I am assuming I copy the whole header.php from the parent twenty twelve theme, and then into the child theme directory? If that is correct, where do I find the child theme directory? You don’t mean the CSS style sheet that comes up under editor as the only option when the child theme is open?

I am assuming I copy the whole header.php from the parent twenty twelve theme, and then into the child theme directory?

Correct.

If that is correct, where do I find the child theme directory?

It’s the directory you just made; /wp-content/themes/twentytwelve-CHILD

You don’t mean the CSS style sheet that comes up under editor as the only option when the child theme is open

Nope.

omg. You are a life saver! Thank you!
That really works.

I still have so much to learn.

Thank you very much.

After all your help I feel bad asking, but if you’re still around,
is there are an easy way to center the header?

The image?

Yes, it is off to the left, but I’d like it to really hover over the middle of the menu bar.

In your Child Theme style.css file, add this;

.header-image {
 display: table;
 margin: 24px auto;
}

at the bottom? leave the rest untouched?

Yes.

It worked like a charm.
I need to hire you.
Thank you!