Make gallery info appear on hover

Site URL: http://www.kirstylittle.com/sculpture-index

Hi, my template is brine and I have a gallery section on my index page. The photos in the gallery all have captions, which I have inserted, but I want them to appear on hover. When I look online for the solution, I'm basically told it can happen (this feature is said to be possible with brine), but the settings of the online instructions don't align with what I am seeing, thus making me unable to solve the problem. I've attached photos of all relevant settings that can be changed in relation to this in 'Site Styles' so whoever can help can see what I am seeing. Please help, this problem has been bugging me for quite some time. Thanks

Add to Home > Design > custom CSS

.Index-gallery-item-content.Index-gallery-item-content--has-title-and-body {
    visibility: hidden;
}
.Index-gallery-item-inner:hover div {
    visibility: visible;
}