Google has posted Android P DP3 (Beta 2) images for the 2016 Pixel/Pixel XL and 2017 Pixel 2/Pixel 2 XL devices. You’ll also be able to install the new build on select devices from Nokia, Vivo, OnePlus, Xiaomi, Sony, and Oppo. Below is the download link and installation instruction for Pixel devices.

If you would like to know what is in store for Android 9.0, join the Android Beta program by going here. Upon joining, you will get the OTA update for the Android P beta. If are reasonably techy, you can also install factory images /OTA manually by downloading the required file. Download Android P DP3 (Beta 2): Pixel (sailfish) – Factory images/ OTA Pixel XL (marlin) – Factory image/ OTA Pixel 2 (walleye) – Factory image/ OTA Pixel 2 XL (taimen) – Factory image/ OTA Installation: After downloading the required file, you may follow this step-by-step guide to install the build on your device manually. Before you begin, you should take the necessary steps to ensure all your data is backed up. [Source]