Updating iOS for iPhone 3G

[wonghongweng]

Hi all,
I have an iPhone 3G which runs on iOS 3.0. It has never been updated. Now that Apple has discontinued support for this phone, how do I update it to iOS 4.2.1?
Please help.
Thank you.

 

[Massie]

Plug into iTunes and click Update. You'll be updated to 4.2.1.