Apple is seeding the iOS 8 update to iDevices. Check iPhone 5S, 5C, 5, iPad, iPad Mini, iPod Touch iOS 8 update process, changelog.

Finally iOS8 gets out of beta after months as iOS 8 update is now rolling to Apple devices. The support devices list includes a number of smartphones and the update will also be available on iPhone 6 and iPhone 6 Plus as well.iOS8 update

This should be compatible with the following Apple handsets -

And as precautionary measures, it's advised to backup data on your device and have 2 GB of free storage for updating. When you are ready check the battery level and then head to Settings > General > Software Update and check for update availability. The new iOS 8 update can also be downloaded by connecting your phone to PC using the iTunes software.