How to get instagram on my iPhone?

I went to the App Store to download Instagram app yet it told me an Update is Required: iOS 4.3.
I don't really know what this meant so I checked if my iPhone needed any updates, but it said it was up to date and it did not need any updates. I went to check again, and it still says the same thing! How can I download the app? Is it my iPhone or something?

Added (1). I already went to iTunes and synced it to it. Yet, it says on the iTunes that the iPhone is up to date still. Or is there a button I'm not clicking on?

Try plugging your I phone into a laptop that has I Tunes and that usually works for me. That should update it, after that go to the store on your phone and download it

You have to update your ipod to get iOS 4.3 software to be able to download it.
So just connect your phone to you computer, update it, and then you can download the app