[Koha] How to add Marc subfields to OPAC results and detail

I have a couple of simple text Marc fields that I need to be displayed in the results and detail view in the OPAC. How do I do this? Do I edit the xslt files in /usr/share/koha/opac/htdocs/opac-tmpl/bootstrap/en/xslt? Are there any examples I can follow for adding a Marc field to OPAC? Thanks, Jonathan