Hey Darien,
You did create that look by adding custom code in Theme Options > CSS. If the home page is the only page you want that header overlay effect, update .masthead
into the code to .home .masthead
Please just note that working with custom code is outside the scope of our theme support. What we can do is just lead you in the right direction or provide some guidance.
If you want to avoid custom coding and have complete control over how the header looks per page or site wide, please consider upgrading to Pro. See https://theme.co/pro
Thanks.