Using the Openfire admin console, you typically do this to import your certificates (although it sounds like you already found this):
Server
TLS Certificates
Manage Store Contents (of the store that you want - by default, everything uses the same store anyway)
“imported here” (that link is hidden somewhat in the text).
If that does not import your certificate properly, something is wrong. Please have a look at your log files (<openfire_home>/logs/all.log combines logging statements for all levels) and see if a relevant message is being logged.
As far as i remember there was an issue with logs not working on Linux in older versions. Could be 3.6.4. It was fixed eventually. I think it was related to s4j log or something.