2) Install the child theme, the installing progress is same with installing a normal theme, the installable file is “air-child.zip”. Activate child theme after installed.
4) If you want to change some PHP files: header.php, footer.php, single.php, page.php, comments.php, searchform.php and PHP files in the template folder, please clone the PHP file, move the cloned PHP file into child theme folder. Please make sure the same folder tree with the parent theme. Like:
You can change the cloned files into child theme folder.