It is important to ensure your server username and password are changed from the default admin and freenas respectively.
To do this, from the Web GUI: Go to System -> General
Username can be changed within the WebGUI section.
There is a Password tab near the top, where the password can be changed.
Remember whenever any change is made, you need to click the Save button near the bottom of each settings page you make any changes on.
Time to adjust the network settings now.