Most Minimall’s sections are editable from your child theme.
As a matter of fact, most files at the root of your theme (header, footer, search, and more) and everything in the “template-parts” folder is customizable in your child theme.
It's not recommended to edit directly the files in your parent theme. Your changes would be erased on the next theme update. Use a child theme instead.
For the purpose of the tutorial, let suppose you want to add the “my-custom-class” class to the main hero.
Start by creating a “template-parts” folder at the root of your child theme.
Identify the file you want to customize and copy it in your child theme “template-parts” folder.
In our situation, copy the content-hero.php file.
Edit the file with your favorite text editor and save it.