This is not really a very difficult process but it was not obvious the first time that I tried it. So here is the step by step guide:

  1. Log into your Apple Developer Account and download iPhone OS 3.0 Beta 2
  2. Open up the downloaded package
  3. Go into Xcode and open the Organizer (shortcut is command-O)
  4. Make sure your device is connected properly (i.e. you have a green light)
  5. Go to your device
  6. Go to the Software Version dialog and select ‘Other Version…’
  7. A file chooser will come up and you can go and find the restore package that you want to install (it should end in .ipsw)
  8. Click restore version
  9. Wait…

And that is it, you have installed the new version.  This does of course wipe out all the data on your phone and sets it to a factory state so beware of what you are doing before you do it.  You probably need to install the SDK along side the OS in order to use all the features so that would also be recommended.

I guess my last piece of advice is that you should take a look at the advisory for the beta before you install the software, it will warn you about the severity of what you are going to do.  Anyway, I am looking forward to developing with all the new fancy feature that Apple is pushing in to it’s iPhone OS version 3 and I know that you are as well.