If you missed the Android Beta last year, this beta program is used for getting the latest builds of Android via OTA, no sideloading and flashing required. As for which devices are supported by Android Beta, Google states that the Pixel, Pixel XL, Pixel 2, and Pixel 2 XL can take part.
To get started, follow the Android Beta link below, select which Google device you want to opt into the beta with, then sit tight for Google to push the Android P beta right to your phone.
Of course, if you want to sideload and don’t want to wait for an OTA, we’ll let you know as soon as the Android P DP2 files are published by Google.
Update: Google is changing things up big time this year, opening to the beta to devices from other OEMs. Full details here.