nobody really knows because samsung is not willing to release any kind of information, and good luck getting in because the amount of people are apparently limited to some very small number, which nobody knows.
The banner on the Samsung Members homepage. You would tap it and it would walk you through the enrollment process. You would be required to have a Samsung account linked to it. But overall, it's pretty easy to enroll. The hard part is spotting the banner and enrolling before the beta is full.