Finding Fourier Coefficients of a periodic data?

I have a periodic data set. Lets say in one column I have angle (0:2*pi) and in next column I have value of potential at different angles. I want to express this data in a fourier series,, therefore I need the coefficients. Someone help me how to determine the coefficients if I have the data set. New to Matlab. help!!

[José-Luis]

doc fft