FFT to a simple sine wave

I have a simple text file with two columns, amplitude and time steps values. i want to apply fft to the signal so that output should look like attached picture. consider just one waveform.

[Dyuman Joshi]

What have you tried yet?

What issues are you facing?

Answer 1

[Star Strider]

I am not certain what the independent variable axis is (the label is cut off), however if you want a power spectral density plot, use the pwelch function.