Users needs to sign an NDA (Non-Disclosure Agreement) with OnePlus to be part of this program. As of today, OnePlus will accept 100 people into this Closed Beta Program, and those chosen will be contacted if they are accepted in the program.
OnePlus has just started Closed Beta program for its newest flagship smartphone, the OnePlus 6. You can opt-in right now and if selected, can get an early access to all the latest Software.
At this point, OnePlus is handeling three builds, Official OxygenOS, Open Beta, and Closed Beta for the OnePlus 6.
Official Builds are just normal OTAs for all the users, Open Beta are for users who want try and test the latest builds, available for public. Closed Beta users receive builds and features weeks or even months before they are released to the public as Open Beta or as Official OTAs.
OnePlus 6 owners can Apply for Closed Beta Right Here!!!