How to calculate PSD if i have power vs freq spectrum? i have a signal something like this

how to calculate PSD?
i have freq from 191000200 to 196500000
time gap or delta t = 1 or 2 sec, (what i mean is [tn] - [tn-1])
i will be computing in python any suggestion from scipy or any lib will be helpful
thanks in advance
i used this formula saw on wiki, https://en.wikipedia.org/wiki/Spectral_density#Power_spectral_density
it works okay for me, 
thanks for the comments, it helped me to understand the data what I was receiving.