Hi Andreu-
In order to interface NI-DAQmx with the System Identification Toolkit you will also need to have SignalExpress installed.
If you have already installed SignalExpress but the steps are not showing up then I suggest uninstalling and reinstalling in order to ensure that all support has been installed for the System Identification Toolkit.
If you do not have SignalExpress or need more information, please check out
http://www.ni.com/signalexpress/Thanks and have a great day!
Tom W
National Instruments