Setting image files as main nav menu items

Hello – I have been trying to follow the tutorial on this page: https://wpmu.org/wordpress-custom-menu-icons/
and I can’t seem to get it to work – I’m having trouble figuring out what the main container is for the nav menu at the top of the page – it looks to me like it should be #menu but that doesn’t seem to be working. This is what I added to my CSS and it didn’t do anything:
#menu .home a {
background:url(‘https://daily-mash.com/dm/wp-content/uploads/2013/02/home.jpg’) no-repeat 0.5em 0.5em #ffffff;
}

it seems like this should be pretty simple to do but I am quite the noob. Can anyone help me out with this? My url is https://www.daily-mash.com – thank you for your help!