How to use an FFT with decimal I32

Hi

I am new to Labview I wonder can anyone help I have used LabJack SPI to pull in samples of my accelerometer 125Hz
I end up with Decimal I32 and can graph it fine. But I have no Idea how to use it with an FFT I think I must have to convert it as most want 1D can someone please advise me.

Many thanks