Sticky Navigation Bar for Ishimoto Template - CSS Help

Site URL: http://www.cowdogcraftworks.com

I've been trying to get some custom CSS to get my navigation bar to be fixed. I see a lot of fixed navigation bar options, but they don't appear to work on the Ishimoto template. Anyone able to help? It seems like a quick fix every time I've seen it.

Add to Home > Design > custom CSS

/* Fixed Header - Desktop */
header#header {
    position: fixed !important;
    top: 0;
    left: 0;
    right: 0;
    z-index: 999;
}
div#pageWrapper {
    margin-top: 100px;
}
/* Fixed Header - Mobile */
div#mobileMenuLink {
    position: fixed;
    left: 0;
    right: 0;
    z-index: 999;
}