Frequency spectrum diagram of PV output power

Hi all, I want to extract the frequency spectrum of PV output power by FFT. The problem is I don't know how. I have the measurements in excel sheet. The first column is the time, the second the measurements.

I tried to use the FFT block in simulink. As input I used the repeated sequence interpolated block, then the FFT block, the complex to magnitude-angle and then a vector Scope. Unfortunately I get nothing!! Is this the correct setup?

I tried to do what they did in that post but I have no idea if that is correct. http://www.mathworks.se/matlabcentral/answers/45844-how-to-use-fft-in-matlab-using-imported-data-in-time-domain-excel-file..

Any help would be appreciated! Thanks in advance George