Apple has been publically released iOS 8 today meaning you should be able to download the update If you happen to have an iPhone 4s, iPhone 5, iPhone 5c, iPhone 5s, iPod touch (5th generation), iPad 2, iPad (third and fourth generation), iPad Air, iPad mini and iPad mini with Retina display.

To Update, just open up the Settings app, followed by the General and Software Update options. Remember this is a gradual rollout meaning the update might delay to appear for some users, just keep checking.