How to draw a spectrogram for my earth magnetic data?

I have a ground-based magnetic data taken every second and i want to plot a spectrogram for my data but i notice that the spectrogram equation on matlab need this parameters [window,noverlap,nfft,Fs] which i don't know. and i notice also that i should do the FFT on my data first before plot its spectrogram.

here is how my data look like, I took about one day and half.