Hazmat is assuming you have a Merlin Mail or 007 Merlin Legend Mail. His instructions are for creating the mailbox in the VM by using a telephone to log into the System Administrator's mailbox and following the prompts to create a new mailbox.
You also need to put the extension in the Voice Mail cover group through SPM.
Menu>System Programming>Exit>Extensions>
More>Group Cover
Now enter the Voice Mail Cover Group (typically 30, but can be any group from 1 to 30)
Enter>Inspect
If at this point you see other extensions that have voice mail listed, you have the right group and press back (if not, go to print and print out the Group Coverage report to determine the VM Cover Group)
Now you're back at the 2nd page of Extension options
Group Cover>30>enter>[Extension No.]>Enter>Exit