Create child theme

This plugin Child Theme Configurator helps us to create child theme easily. Here is some quick steps:
1.1 Install & activate that plugin
1.2 In Admin menu, click on Tools >> Child Themes
1.3 Select options as below:

then click blue button at bottom of page.
1.4 For Genesis themes, please skip this step.
Otherwise, please click on Files tab to copy relevant files from parent theme to child theme:
childtheme-2
It all depends on your need to select what files to copy. If you only want to replacing layout in Category page, you should select category or archive. If these 2 files were not existed, please select index.

1.5 Finally, activate this child theme on Themes page.

Best regards,