I've never tried to use a custom certificate but you can perhaps find some usefull things there:
Thanks for taking the time to look into this. The link you posted points out that we can convert a .key file to a .pem file, which is useful to know. Unfortunately, we don't have any .key files at our disposal. Is this something that I need to create individually/separately in the Microsoft CA? If so ... how?
Thanks again for your time!