Hello @allison-nordling,

To display the latest post in the featured content section you have to create and activate the child theme.

https://codex.wordpress.org/Child_Themes

You can also create the child theme using the plugin. Below is the link to one of them.
https://wordpress.org/plugins/wp-child-theme-generator/

After activating the child theme in your child themes functions.php file paste below given code:

https://gist.github.com/anonymous/6d8bc94d7a28f361981510f9a09eed5b

Also make sure to chose the option Featured Posts from Admin Panel > Appearance > Customize > Featured Content > Featured Content Type > Select Type . It will only work upon choosing this option.

Hope this helps.

Best Regards!!