It was widely expected that Google will announce the next iteration of Android, called the Android N at its Google I/O. However, Google has shocked everyone and dropped the Android N-bomb well in advance. The update was released last night as a Preview Build was released largely for developers so that they could check whether their apps are compatible. Google also announced the Android Beta Program, where those interested, can try out the latest Preview Build and provide their feedback.
Once you are a part of the Beta Program, you will be allowed to enroll your device in it, if it is supported and via an OTA you will be sent the latest Preview Update. Unfortunately, the devices supported are fairly a small group, mainly of just the Nexus devices. There is one Android One device in there. Currently, only the Nexus 5X, 6, 6P, 9 and Pixel C are supported. So if you have one of these devices and would want to try out the all new Android N, here is how you go about it.
Head over to the program page here and login using your Google ID which you have active on the supported Nexus phone. Once you do that, you will get the option to enroll the device. Do this, and you will receive an OTA update with Android N just like any other normal OTA update. Let the system install Android N on your system and you can then enjoy features like multi-window support, night mode, new Settings app, revamped Notifications bar and more. In case, you find the Preview Build is too unstable for your liking, it is very easy to revert also.
All you need to is, go back to the aforementioned link, and simply withdraw your enrollment. The moment you do that, Google will send you an OTA update with the latest stable release for your device. It will wipe all your data, but your phone will be back to a stable Android version. As simple as that.
So why wait, if you have one of the supporting Android phones, go ahead and update.