create wp child theme
Let's create a child theme for the TwentyTwentyOne theme:
1) Create a new theme directory:
/wp-content/themes/mychildtheme/
2) Create a style.css file inside the new directory
(/wp-content/themes/mychildtheme/style.css) and add the following code:
/*
Theme Name: Twenty Twenty One Child Theme
Theme URI: https://www.mysite.com/
Description: A Twenty Twenty One child theme
Author: JustMe
Author URI: https://www.mysite.com
Template: twentytwentyone
Version: 1.0.0
*/
@import url("../twentytwentyone/style.css");
3) Go to Appearance > Themes and select the newly create child theme
4) Done!
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References and further study
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How to Create and Customize a WordPress Child Theme
https://www.hostinger.com/tutorials/how-to-create-wordpress-child-theme
Child Themes at Codex
https://developer.wordpress.org/themes/advanced-topics/child-themes/
How to Create a WordPress Child Theme (Video)
https://www.wpbeginner.com/wp-themes/how-to-create-a-wordpress-child-theme-video/