Can I update my iphone 3gs to an ios 6? And if I can how?

Have tried to update it by connecting it to iTunes but it doesn't seem to work!

Yes I just checked Apple site it says iPhone 3GS can run iOS 6

http://www.apple.com/ios/whats-new/ go to the bottom of the page and you see that iPhone 3GS is compatible with iOS 6.

good for you~

Steps on updating firmware:

1) Connect iPhone to iTunes

2) In iphone summary click check for updates. A pop up will appear saying 'A new update (iOS6.) is available for your device'… Bla bla.

You click 'download and install now' and itunes does the rest…

3) Done.

I don't see why it wouldn't.iOS 6.1.2 is supported on that iPhone. Are you sure it is an iPhone 3GS? The iPhone 3G looks the same externally but that can only update to iOS 4.2.1.