OK, Its public version will be available starting from October 12 for all Apple’s devices, which means 2 days only of waiting. But in case you can’t wait here is the way, only in case of any problem happened please Back up your iOS devices with iTunes.
Step 1: Download iOS 5 GM firmware from any safe site (Google Search .. Download iOS 5 GM).
Step 2: Download iTunes 10.5 beta 7 from links below:
Download iTunes 10.5 beta 7 for Windows 64 bit (link)
Download iTunes 10.5 beta 7 for Windows 32 bit (link)
Download iTunes 10.5 beta 7 for Mac (link)
Step 3: Open iTunes then to your iPhone settings and hold down the option key on a Mac or the shift on Windows and click the Restore button. Point iTunes to your iOS 5 GM IPSW file you downloaded then wait for iTunes to finish.
Step 4: Restore your device from your backup to get your data back on the new iOS. It will be rebooted once then you’ll get your device ready to use.
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