data = Import["~/Downloads/getwfm(2).isf"]
data2 = Most[data]
p = ListPlot[data2, Joined->True]

n = Length[voltages]
w[x_] := (0.5)*(1 - Cos[(2*Pi*(x-1))/n])

voltages = Table[data2[[i, 2]], {i, 1, Length[data2]}]
f1=Fourier[voltages]
windowed = Table[voltages[[i]]*w[i], {i, 1, Length[voltages]}]
f2 = Fourier[windowed]

ListPlot[Abs[f1], Joined->True, PlotRange->{{190,210}, {0,150}}]
ListPlot[Abs[f2], Joined->True, PlotRange->{{190,210}, {0,150}}]