[Koha] KOHA XSLT

Dear community, i am currently in a dilemma. I would like to add a separate view of MARC21 and ISBD on the intranet, one that shows me my records in APA and ISO690 format. Thanks to your contributions I can understand that I need to create an XSLT template, but I do not know the location where I should go and how it should be composed. Would greatly help your contributions to my problem.