- Acme Themes

Dear mariettedietz,
The link is wrong. You are not using WordPress.Com theme, you are using WordPress.Org theme and every file of theme you have inside your WordPress installation folder. public_html/wp-content/themes So check that file and check your style.css as mentioned above.
Above css need to put inside Appearance > Customize > Additional CSS of your site. First login to your dashboard, you will get the options.