starting with FFT megacore function

Good morning everybody, I'm new with altera devices and I would like to use my Stratix II FPGA as a FFT Spectrum analyzer. I have looked for information about the FFT megacore function, and there is a lot about its implementation with the wizard, but not so much about how to use it.

I'd like to intruce a signal on the ADC with a signal generator and extract files with 1024 samples fft results. My problem is that I don't know how to use the outputs of the fft module and what is more important, how do I save these results in a file? With signaltap II it's easy to introduce time domain signals into files, but in this case the signal is on frequency domain and I don't know how to do it.

Please if somebody could also explain me what information is exactly contained on the 'exponent' output of the fft module, it would be very helpful for me.

Thanks a lot for your help.