I have the correct CSS code to change the cover images of my cave(s) because I use the Google add on called "Live CSS Editor" but I have no idea where to put the code. I've tried it in the den desc, cave CSS spot, and cave desc, but nothing is happening. I've looked up other methods but they don't work and I don't want to buy DropBox. Also with the cursor.

My code is:
a[href="cave.php?id=296316"] > div.cave-grid > img {
background: url('https://i.postimg.cc/261dz8VS/barton-creek-cave-belize-COOLCAVES0220-0bc894a65bb84a0899ef38ea085935aa-7.jpg') !important;
padding-left: 100%;
height: 120px;
}

Cursor code:
{cursor: url(https://cur.cursors-4u.net/nature/nat-8/nat733.cur), auto !important;}