To install iOS 8 Beta 3 in any of the iOS devices are two very simple ways. The first is when you go to install the Beta3 version for the first time on iPhone and iPad, for this we recommend downloading the appropriate link to your device and then you follow the steps in our tutorial to install the Beta version 8 iOS iPhone, iPad and iPod touch.
Moreover, if you already have installed the Beta 2 of iOS version 8 on any of your iOS (iPhone, iPad) devices to test the Beta 3 just have to update through the same device via OTA, with the following steps:
Settings> General> Software Update
At this point you just have to click on Download and then install, the device will ask for the security code on the device, you enter, you accept the terms and conditions, and then let the device update only.
Note: iOS beta 3 8 functions with iPhone and iPad (with 3G or 4G connectivity) Orange, Vodafone, Movistar and other mobile operators. It is important to download the version that corresponds to the device you have to avoid any failure. If the device is locked by the operator, this will only work with a SIM card of the corresponding operator.