Android betas are granted to a Google account.
Tell us the Google account on the phone you'll test with, and we'll grant it access to the Kiren beta.
We'll grant that account access to the Kiren beta and email you as soon as it's ready to install.
When you get that email, make sure the Play Store on your phone is signed in as this account before you tap the link. If it's signed in as a different account, the beta won't show up.