1. Make sure your iTunes is updated to the newest Version.
If your iPhone was Jailbroken, you WILL have to use DFU mode to update to iOS 8 (or to reinstall 7.1.2 if you have an iPhone 4).
DFU mode helps when your iPhone won't restore or is stuck on Apple Logo or itunes Logo, or if you want to jailbreak your device.
Works on: Windows XP, Vista, Windows 7, Windows 8, Mac OSX
iPhone 3G 3GS 4 4S 5, 5S, 5C, iPhone 6, iPhone 6 Plus, iPhone 6s, iPhone 6s Plus
iPad, iPad 2, New iPad 3, iPad Mini
iPod Touch 1st 2nd 3rd 4th 5th Generation
iOS 4, iOS5, iOS6, iOS7, iOS 8.0, 8.1, 8.1.1, 8.1.2, 8.2, 8.3, 8.4, 9.0, 9.1, 9.2, 9.3.2
2. If for some reason you do something wrong, and the "phone won't switch on" anymore, meaning the screen stays black. Just hold both the home and power button for about 20 seconds. The phone should switch on again.
To solve Error 3194 on Windows:
1) Update iTunes to the newest version!
2) Go to the following folder:
Delete the hosts file in there (if you have any illegal programs on your PC, you have to edit this file - don't delete it)
Close and reopen iTunes. Now error 3194 should be resolved.
IF YOU HAVE TROUBLE WITH THIS, try my other other video: www.youtube.com/watch