Google has released Android 7.1 Developer Preview (NPF10C) for Nexus 5 X, Nexus 6P and Pixel C with new features like launcher shortcuts,
round icons, image keyboard support and more. People who have already signed up for Android Beta program will receive the Android 7.1 Nougat Developer Preview OTA updates (Android N-MR1) on their device, which weighs around 1260MB. Other users can install the factory image manually.
Currently, the update (Android N-MR1) is available only for the Nexus 6P, Nexus 5X and Pixel C. It is expected that the update will be available for other devices beginning sometime in November. Android 7.1 Nougat is the next major OS update, as it includes various new features, performance tweaks as well as API changes for developers.
Android N-MR1 update (NPF10C) weighs around 1260MB. You can enroll your supported device in the Android beta program [HERE] to get the OTA update on the developer preview or download the factory images and flash them manually.
If you have difficulty in downloading the OTA update on your device. Follow the manual installation method. This method will ERASE your device, so make sure you have backed everything up first. It is recommended for tech-savvy users only.
1. First, download the Android factory image (developer preview)for your device from here
2. Setup ADB and fastboot drives on your PC and follow the flashing instruction as described here
Note that, this is a developer preview, so it can contain bugs that can affect normal functioning of the device. (Source)