If you haven’t signed up yet, go to beta.teamspeak.com and sign in with your myTS account. When your time comes, the Testing Badge will be automatically assigned to your account, but you won’t be notified, so you’ll need to check your badges or beta access on beta.teamspeak.com from time to time.
Also, I highly recommend taking a look at this thread which explains a lot of things about the Closed Beta.
