It certainly is possible to perform FFT in Excel, however, we don't have instructions on how to do this.
You will need to lookup how to use add-ins within Excel's help files then load the appropriate add-in (there's one which has an FFT function) and learn how to use it within Visual Basic for Applications. Its not a particularly quick or easy thing to do though.
The quick method is to use the spectrum view in PicoScope, then save the waveform as a TXT file. You can import this as a tab delimited file with the Excel import wizard.
Pico Software Engineer