Usually this shows up in the Samsung Members App for eligible phone's, to which you can then apply to join the Beta.
Just be mindful that Beta by it's very nature is buggy , causing lag and some features to not work as they should so I wouldn't recommend to download a Beta onto your daily driver.
There is some general information in this Samsung link.
Daily Driver > Samsung Galaxy s²² Ultra 256Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help. " This is the way. "