Code for custom bullet points (checkmarks)?

Hi there, I'm hoping to add some custom checkmark bullet points to my site. I wish Squarespace already had the option to do this without custom code!

I found some code in a YouTube video, but it didn't work for me. My website is Personal, not Business - not sure if that matters.

If anyone has a piece of code for checkmark bullet points, I'd love to try it! Thanks so much.

@amandaclairef You should be able to still add code to the Custom CSS area, under Website Tools, even just on the Personal Plan. It's mostly Code Injection, if I'm not mistaken, that doesn't work. 

First, you'll need to upload the image you want to use for your check marks. Upload it within the Custom CSS area. I've attached the one I've used to this post. 

Then you can use this code, and use the link from the file you just uploaded where URL is. 

ul[data-rte-list] li>*:first-child::before {
    content: " " !important;
background-image: url();
  background-size:contain;
  background-repeat:no-repeat;
  background-position: center;
  height:20px;
  width:20px;
}

Let me know if this works for you!