How to Add A Custom.css File to a WordPress Child Theme

Create custom.css file in your child theme and paste in this code with the correct information, and place your custom css code below.

/*
Theme Name: 
Description: 
Author: 
Author URI: 
Version: 
Template: 
Template Version: 
*/

Next, add the following snippet of code to the child theme’s functions.php file.

// CUSTOM CSS FILES
function custom_style_sheet() {
wp_enqueue_style( 'custom-styling', get_stylesheet_directory_uri() . '/custom.css' );
}
add_action('wp_enqueue_scripts', 'custom_style_sheet');

Voila!