Applying a Plot to cftool

Hey! Please help.

I am relatively new to Matlab and I would love some help. I have a random 5x5 binary code with zeroes and ones. With that I have plotted it using:

x=randi([0 1], 5);

index = find(1);

x(index) = [];

stairs([x,x(end)]);

print('tempplot','-dpng');

Which looks like the attached file. With this function/plot now I am trying to apply the Fourier Series Approximation using cftool (which I have). But every time I do it it says "Input must be two, three, or four variables or a curve fitting session file." I am trying to find the approximation of this function. Is there a way around it? Someone please help! I very much appreciate it in advance.