Wait! When I signed in, the app didn’t ask me to set a password. What’s up with that?
Circles does not use passwords. When you sign in for the first time you will get an email to the email address associated with your Circles account containing a six digit code. Enter that code the first time you sign in. Search for firstname.lastname@example.org in your email if you can't find it right away. You will only have to login again if you sign out or get a new phone.