Install Virtual Appliance
The FreeNATS virtual appliance is based on the rPath (www.rPath.org) LAMP appliance and is a VMWare (Player, Server etc) compatible VM image with a default 256Mb of RAM and bridged networking.
Download the current virtual appliance release from http://www.purplepixie.org/freenats
Run the virtual machine with the software of your choice. The system should get an address off the network via DHCP.
Once booted instructions on how to connect to the device via IP address should be displayed on the console.
The first time you boot the machine you should login via the console as root (password freenats). A firstrun script should then execute prompting you to change the root password and telling you how to proceed.
It's a very good idea to run the upgrade script (/root/freenats/upgrade) at this point to make sure you're running the latest FreeNATS software version. For packaging reasons the current virtual appliance is often not pre-installed with the latest version of FreeNATS. Further information is available in the "Upgrading FreeNATS" section of the documentation.
You should login to the rPath administrator via your browser at https://YOUR.FREENATS.HOST:8003 (username admin, password freenats) and change the admin password immediately.
You may wish to setup the timezone as different from the (GMT) default. You can do this through the rPath interface (and should ideally reboot the appliance afterward).
Login to FreeNATS
The FreeNATS system can be accessed via http://YOUR.FREENATS.HOST and you can initially login as admin (password admin).
The virtual appliance is already configured to run the tester every minute (with appliance 4.0 or later - five minute intervals in previous appliances) and the cleanup script daily as well as monitor itself (node freenats).
Ongoing Maintainance / Working with the VM
You may like to the the virtual appliance section of the documentation for some pointers on maintainance.