Owners of an Essential phone now have the option to opt-in to receive beta updates OTA from Essential. This is way better than having to sideload the build onto your phone in order to try out the beta builds. This helps especially now that the beta builds are Android Oreo updates, so you get to check out the new Oreo features, all using an easier update method.
The process to sign up to receive the beta OTA updates is fairly simple. All you have to do is go to Essential's site and choose to receive your update through the Over-the-Air method. You will then have to fill in your information, the most important part of this being your serial number so they know which phone to send the update to.
Sideloading is still an option for people who like that method better and don't like to receive every single beta update. Although both methods accomplish the same thing, it is a personal choice, in my opinion the OTA update is a better choice because it removes the hassle of flashing the update using recovery mode.
If you ever decide you want to go back to a stable version there is an option for that on the site as well. All you have to do is re-enter your information and your serial number and you'll receive an update which will revert you back to the stable version. Hopefully, you won't have to wipe your phone like in OnePlus' case.