Simply browse to the IP address of your ReadyNAS in your web browser, adding /NEURAL/ (capitals are required) to the end.
For example:
http://192.168.0.10/NEURAL/
You can find the IP address of your ReadyNAS on the LCD screen (for models with LCD's). If your IT service provider installed the addon for you they may also have provided the IP of the NAS on the front of the documentation provided.