How to update ISO on Live View mode on the Nikon D5100?

So every time I change the iso, it's not updating in Live View mode like on the Canon. How do I make it update? Because when I change the iso nothing happens.

When you change the ISO using the ISO feature on your cameras menu, when you switch to live view, the same ISO should be shown there.

If you are shooting video, the camera picks the proper ISO so that the exposures you get at a specific fps and lens aperture are properly exposed.

How much time have you spent looking in your user manual, especially under the ISO pages?

ISO can only be manually set in certain modes of any dSLR. Read the manual to learn which modes you can work ISO with.