Apple has rolled out update for iOS 8. So if you are running iOS 8, you should get a notification in Software Update section about the latest update. In case you aren’t sure where the Software Update section is, simply tap the following icons on your screen.
Settings > General Software Update
Please make sure you backup your phone before applying the update.
NOTE FOR JAILBREAKERS: If you have jailbroken you device, stay away from this update until there is an update from Pangu team. As of right now, if you move to iOS 8.1.1 you will lose jailbreak.
The good thing about this update is that iPhone has still not forgotten iPad 2 and iPhone 4s. And this update focuses on these old devices in order to improve the iOS 8 experience.