I am working on a Beaver Builder theme with a child theme and I am not sure where to put the three line code you specified for the breadcrumb plugin. You have a snapshot of where it should go but looking in the theme editor for the child theme of course there is no theme header.php file. When I look through the parent theme I had trouble finding that spot. I want to avoid deadly white screen. Please advise.
I will add that I am not well versed in procedure..should I do this via FTP or the admin end of the site?