If you want to override how LearnDash outputs dynamic content, you have to add a file of the same name into your theme or child theme. For example, if you want to change how the infobar content is displayed, you need to edit the infobar.php file. All that is needed is to place your php file in the correct folder.
If you’re overriding the file:
/wp-content/plugins/sfwd-lms/themes/ld30/templates/modules/infobar.php
then the file in the child theme will be:
/wp-content/themes/xxx-child/learndash/ld30/modules/infobar.php