The user credentials info is shown on the Default Credentials (Passwords) for NMIS8 VM page, which covers both the Opmantek Virtual Appliance and the case of a standalone NMIS. In the NMIS-only case the "NMIS Web Users" section on said page is the only relevant one.
The Open-AudIT credentials can be found on the wiki at Information about default users and passwords.
Try the following link.