How do I update my iPhone 4 iOS from 4.2.8 to a newer version?

You must be running the latest version of iTunes first. If you are using a Mac, you must have OS X 10.5.8 or higher.

You need the iTunes update first.

After that is installed, with your iPhone connected select check for update under the Summary tab for your iPhone sync preferences with iTunes.

First of all you need the newer version of itunes goto itunes a message might pop up saying theres a update avalible for itunes then when its done updating, go onto the iphone tab then go on summary them on version there should be a button saying update wait for it to update then your good to go

What version of OS X are you running? You MUST have 10.5.8 or later.

Before even updating your iPhone, makesure your iTunes is updated and is at its newest version. (If you're a mac user; open itunes > press iTunes on the top bar which is next to the apple icon, then press check for updates.)

Once in a while there should be a pop-up message informing you that there is a newer version of iTunes, if you do not receive any at ALL, you probably pressed 'Do not ask again' when you saw one before. After updating your iTunes, plug in your iPod/iPhone into the computer and press the ipod name that appears at the side bar of the iTunes window, at the page where it shows your Serial Number/Code and the information of your ipod (including its' name and all that), look for the restore button, if you see that, on top of the restore button should be a button that says Update. Press the update button if the function is available and your iPod/iPhone should start updating (there will probably be some Terms & Condition window popping up, but.. come on, I mean, who reads it anyway? 😉 )

Hope this helped! 🙂