Labview inverse Fourier transform: Why can't I visualize Gibb's effect (or ringing)?
You need to restrict the number of harmonics used when reconstructing the original signal else, it'll look just like the original. The Gibb's effect is all about not using the full spectrum. Wiki explains this well. Here's a reconstructed square wave using 125 harmonics: -

And here's the same but only using 5 harmonics: -