Hi najat:
Is there a model number on your instrument? Do you know how it communicates to the computer? As in, is it connected to your serial port? Do you have the manual for the instrument? If not, do you know the commands you need to send the instrument? It will be hard to continue on without this information, however, if you want to a basic example program to show you how this works, you can find an example called Serial Communication in NI Example Finder. The NI Example Finder can be accessed by going to Help->Find Examples.
Emilie S.
Applications Engineer
National Instruments