Quick steps on how to create a child theme in WordPress.

You can do all of this on your machine then upload the folder to your web server typically at public_html/wp-content/themes

My Theme is called Divi

Create a folder (example: Divi-Child)

Create a text file called style.css and paste the following into it and save:
(Be sure the line that says Template has the theme you want as the master theme. Go to Appearance>Theme to get the name.)

Theme Name: Divi Custom
Theme URL: http://yourdomain.com
Description: Divi Custom Child
Theme Author: Your Name
Author URL: http://yourdomain.com
Template: Divi
Version: 1.0.0
Text Domain: Divi-child

Next create a file called functions.php and paste the following into it and save:

add_action( ‘wp_enqueue_scripts’, ‘enqueue_parent_styles’ );
function enqueue_parent_styles() {
wp_enqueue_style( ‘parent-style’, get_template_directory_uri().’/style.css’ );

Any custom code you add you should add above ?>