Attaching navigation menu to bottom of header

I am not sure I should post here or to the theme developer or at some other support forum or ask a question on a blog about this.

I have made a child theme from the ‘Social Triggers Theme for Zippy Courses’ which is, as the name states, a theme meant to be used with the Zippy courses plugin. These are not free items, so they are not in the WP repository.

The parent theme comes with one navigation menu set above the header image and I wanted another–a primary one–set attached or just at the bottom of the header.
I followed the instructions here and with help by commenting I was able to add a second menu (and a couple extra in case I want them later) and almost get it below my header. That is where the problem is now and maybe I should just comment again at that post.

I used css code from my non wordpress website to create the menu–since I want them to match, though it may have some alterations now.

Here is the code

}
/*1670*/
.top-nav {
    position: absolute;
    top: 0px;
    border-right: 0 solid #a5dcc2;
    padding: 0;
    margin: 0 auto;
    margin: 0 0;
    margin: 0;
    width: 100%;

}

There are a few more classes to get it designed, but in googling how to attach the nav bar to the bottom of the header, I keep seeing this basic area I already have created as the solution.

I have tinkered with top: 0px;
First it was -130 and on the public pages that set it in the middle of the header, but on the pages in the student area is set it just below–prefectly–although I would also like the background to span the width of the site.
On my main site the top (I assume) is being measured from the top of the website, but in this site it is not working like that. How do I fix this?
It seems that it is measuring from some other point … fixed point? But what? And Why? How do I get it measured from something that includes or is somehow relative to the header so that it is consistent on all pages?

And then, how do I get it to span the entire width–since this theme is doing that–and if I had a container instead, how would I get it to position within the container and span only that?

Site: theherosspouse.com/community