Hi,
I looked through the instrument driver functions and couldn't find any special functions to retrieve the FFT from the scope. Which means that the FFT trace should be retrieve from the scope like the time waveforms, uising the Read Waveform VIs. Refer to the scopes user manual to determine how the scope returns the FFT trace, this will give you an idea on what instrument driver functions are used.
DiegoF
National Instruments.