Step-by-Step Guide
To start off, back up your device, and download the latest version of iTunes. Next I want you to download your .ipsw in the background because this is probably the longest step depending on your internet connection, which you can download from the list below. I only linked the fastest links below so you should have it within half an hour, and for those of you that are new to this, this is the actual file that contains iOS 8 Beta 1. If you're on Windows you will have to extract the .ipsw and to do so click here for a video to show you how and then come back to this guide.
So now that you have downloaded the .ipsw, and backed up your device, launch iTunes and hold either the Option key if you're on Mac or Shift key if you're on Windows and locate that big file that you just downloaded, the .ipsw. Now just click yes, ok, or accept and now it's all in iTunes hands. Just stick around for about 30 seconds and you will see you iDevice go to a black screen, an iTunes logo will pop up and then it will turn black again and you will see the iTunes logo once again. Congrats you did it!
Downloads:
iPod Touch 5th Generation
iPad 2 Wifi
iPad 2 Wifi (Rev A)
iPad 2 GSM
iPad 2 CDMA
iPad Mini (A1432)
iPad Mini (A1454)
iPad Mini (A1455)
iPad 3 GSM
iPad 3 Wifi
iPad 3 CDMA
iPad 4 (A1458)
iPad 4 (A1460)
iPad 4 (A1459)
iPad Mini (A1491)
iPad Mini (A1490)
iPad Mini (A1489)
iPad Air (A1476)
iPad Air (A1475)
iPad Air (A1474)
iPhone 4S
iPhone 5 (A1429)
iPhone 5 (A1428)
iPhone 5C (A1507, A1516, A1526, A1529)
iPhone 5C (A1456, A1532)
iPhone 5S (A1457, A1518, A1528, A1530)
iPhone 5S (A1453, A1533)