Adding sticky header/nav to Jaunt Theme

Site URL: https://www.sanguisornatus.com/

Hi,

I'm trying to get my menu to be transparent and fixed at the top on the Desktop version of my site. I have this setting working on Mobile but every CSS customization I have tried for the Desktop version hasn't worked. Any insight would be most helpful, thanks!

Add to Design > Custom CSS

body.homepage header.Header.Header--top {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    z-index: 999;
}