Voicemail for UNISTIM devices

I have been able to get all of my SIP devices setup with voicemail but how do I setup mailboxes for my UNISTIM devices.

I had to create the extension in unistim.conf and i defined
and I edited extensions_custom.conf for dialing…

I’m just not sure how to create the mailbox, password etc… Also do i need to define a CFNA routine?