If you’re customizing the theme and want to override theme function, we’d suggest you to use child theme instead of change the original code. Benefit? It help you to prevent the change when you need to update the theme

In this case I will give an example of Modernize. If you’re using other themes, just change the name ‘modernize’ to yours.

1.) Create a new folder in folder ‘wp-content/themes/’, you can name anything.

2.) Create the file ‘style.css’ and put this code inside

/*
Theme Name: Modernize Child Theme
Theme URI: -
Description: Modernize WordPress Theme
Template: modernize
Author: Goodlayers
Author URI: http://goodlayers.com
*/

@import url("../modernize/style.css");

3.) Now, in ‘Appearance > Themes’, You can see this child theme in theme list. Just activate it.

4.) From now, if you need to modify the theme, you can put the code in style.css in childtheme folder directly.

Hope this help everyone