If you have been accepted into the program then right now there are technically two groups you can be in. You can either do the general preview group or you can opt for the new dashboard/os group that they have to test the new Windows 10 dashboard. They
should have sent you info on how to do all of this. Check your messages. You do everything you are asking about in the preview app.
Hello last night I had a system update for the OP and it was at the point it said do not turn off and my power went out and when the power came back on it just says x box one with a green screen and its been this way since 2 am