How Do I Get Rid of Dark Box over Feature Image?

Hi there, give this a try to remove the overlay on featured images on single posts:

.entry-hero::before {
  background-color: transparent;
}

Don’t edit the theme files directly, otherwise your changes will be overwritten every time the theme is updated.

An easy way to add custom CSS is to install the Jetpack plugin and activate the Custom CSS module. You’ll then add your custom CSS in the new stylesheet editor that’ll appear in your dashboard, under Appearance > Edit CSS. You could also install a standalone custom CSS plugin if you prefer.

If you need further help, could you provide a link to your site so we can have a look directly? Thanks!