Please provide the account you want to use. Do not provide your email address: I'd use email@example.com instead of firstname.lastname@example.org, for example. You will be redirected to your instance. There, you need to authorize the Trunk application to act on your behalf. If you do, Trunk will proceed to follow Atheist. If you prefer not to do that, no problem. Just go back to the list and go through the list manually.
Trunk Source Admins Help Alex Schroeder