Mozzy signs you in with the exact same email and password as the website's Backstage — there's no separate app account to create.
Type the email address your band has on file for you. The app looks it up automatically — there's nothing to select or type for "which band" at this point.
If that email is registered with several Mozivio bands, you'll be asked which one to sign into first. You're not choosing forever — see Using multiple accounts on one device to add the others afterward and switch freely.
Same password as the website. Forgot it? Reset it from the website's Backstage login page (Forgot password) — the new password works in the app right away too, no separate reset needed there.