1. Hold down the Sleep/Wake button until Slide to power offappears, the slide.
2. Hold down—and keep holding down—the Home button on your iPhone.
3. Plug your iPhone into computer.
4. Continue holding down the Home button until the connect to iTunes screen comes up
5. Click Restore on the iTunes popup.
6. Click Restore and Update to confirm.
7. Click Next on the iOS 8.4 Software Updater.
8. Click Agree to accept the Terms and Conditions and start downloading iOS 8.4.
9. Select Restore from this backup in iTunes.
10. Choose the archived backup you made before installing the iOS 9 public beta.