I hope no - do it from your PC/laptop - your Google account should do the rest. Then just update app on your HU from Playmarket. Should work this way, but it is only my guess - I did not apply for beta testing myself yet.
Later edit: works both ways.
You was right...
I just registrated on my computer, and then when I start my car head unit and hit the Car Launcher it ask for to update to meta test.
I did, and terrible things happend.
The screen got black every time I tryed to do any setting changes.
Had to turn off the head unit and restart it.
And when I klick the buttons for everything, nothing happens, just got message "Press long press for settings"
But when I did, I inly got the button logo big in center but nothing happend.
Got no settings.
So I have left the beta test panel.
It looks very nice, so when it is released, I think I'll install it.