Fixed header above main navbar?

I am messing around with a blank-t3 template.
I know I can add

.navbar-fixed-top

to

to get the main navigation to "stick" to the top of the window. I'd like to have the logo and search section stay above the nav and have the main navigation stick to the bottom of that. Using devtools I can drag the inside the

while giving the body

top-padding: 150px;

. This all works but knowing that the header.php and mainnav.php are separate what is the proper way to execute this in the template? Still learning, just looking for some guidance.