How to configure folders with ‘Child Theme’?

If you want to override existing parent’s css file, create the exact same file with exact same path and it will override it.

Example: parentTheme/css/awesome_style.css

To overwrite it you should create: parentTheme-child/css/awesome_style.css

More info: Child Themes -> Template Files

You could also add rules to the existing css, you can read more about it in Template Hierarchy

Or if you want to get stylesheet directory URI, you can use get_stylesheet_directory_uri().