Hi Kim,
Thank you for the credentials, for the custom underline please add this to Theme Options > CSS
/*custom underline in menu items*/
li.menu-item a:hover span {
border-bottom: 3px solid transparent;
padding-bottom: 15px;
border-image:url(https://alisonljames.com/wp-content/uploads/2019/06/Merlin-page-indicator.png) 30%;
}
More about CSS border-image Property
If you want to remove the default red line above menu items, please add this as well.
/*remove the default red line above the menu items*/
.x-navbar .desktop .x-nav > li > a:hover, .x-navbar .desktop .x-nav > .x-active > a, .x-navbar .desktop .x-nav > .current-menu-item > a {
box-shadow: none !important;
}
Regarding your header background-image, please update your custom CSS code to this:
/*header background-image*/
.x-navbar-inner {
background-image: url(https://alisonljames.com/wp-content/uploads/2019/06/ALJ_Nav-Bkg.png);
background-repeat: no-repeat;
background-size: cover;
background-position: bottom center;
}
More about background-size and background-position CSS property.
You can find the proper CSS code selector using the Chrome browser Developer Toolbar
For the CSS code itself, I suggest that you get started with this tutorial
Hope it helps,
Cheers!