Hi again,
To add a body class on a page, click on the gear icon in the left sidebar in Cornerstone and then under Page Settings > Meta Settings add your custom class in Body CSS Class(es) field (see screenshot)
Alternatively you can edit your page in WP page editor, under Page Settings metabox you can add your class in Body CSS Class(es) field (see screenshot)
Another approach you can follow is to find the page ID (see https://theme.co/apex/forum/t/setup-how-to-locate-post-ids/59) and use it to hide the carousel on that specific page e.g to hide it on your Contact page you can use this code:
.page-id-79 .x-post-carousel {
display: none;
}
Your Contact page has the ID 79 so the above code will hide the Carousel on that page only.
Hope this helps!