I use an iPhone 5
I have the io7 and I wana install the io6 back old version how?
Whilst iOS 7 is in beta, this procedure will be a lengthy one. You'll need to obtain the iOS 6 firmware file and restore the iPhone to that.
1. First download the most recent firmware file for your device. Save it somewhere easy to access such as your desktop.
2. Launch iTunes on your Mac or PC.
3. Now you'll need to plug in your device and put it in DFU mode, NOT recovery mode.http://theiphonewiki.com/wiki/DFU_Mode Make sure the screen is black and does not say connect to iTunes. This is recovery mode, not DFU. Try again until you successfully achieve DFU mode and have a black screen before continuing.
4. Once you're device is in DFU mode, you'll see a message pop up from iTunes saying the device can't be used until it's restored. Just click Ok.
5. Now hold down the alt/option key (Shift for PC users) on your keyboard and click on Restore iPhone in iTunes.
6. Navigate to the firmware file for iOS 6 that you saved in the first step and click Open.
Now just let iTunes do its thing and if all goes according to plan, your device should eventually reboot and be downgraded to iOS 6 again.