FFT (Fast fourier transorm)

I currently have over 3000 lines of data to interpret due to hand in very soon

I have been using this site,

http://www.ehow.co.uk/how_4670778_fourier-transform-fft-microsoft-excel.html

which has helped a little but I am still having issues. 

when I try and select the input data it says the values should be a power of 2.

can anyone help resolve this?

thank you in advance