Overriding a template, and using php snippets, are different. In the child theme’s functions.php file, you can insert snippets. There is a lot of official HivePress snippets >HERE< or you can make your own. If you use any snippets, never use: defined( ‘ABSPATH’ ) || exit; or php tags: “<?php" and "?>”
To override a template, look >THIS< topic, where you can see, how to override a specific file (user register link).