Thanks for the tip, wroot!
I placed my .crt and .key files into the directory that the “Certificate Manager” is designed to check.
I also have the option labeled “Delete files from the hot-deploy directory after installation” checked-off. However after restarting the (Certificate Manager) plugin my 2 files (still) remain in-tact within this directory.
Also, I don’t think I WANT to add my SSL cert to the “Openfire identity store”.
I just want to assign the certificate to the HTTPS service, so when I navigate to https://hostname.domain.com:9091, the web browser will not display a message saying “untrusted site”.