How do I sign in?
On the web, there are three ways: email and password, Google, or a one-time code sent to your email. The iPhone app offers the same three, plus Sign in with Apple.
As long as the same email is used, it's the same account no matter how you sign in. You can set up or change your password any time in Settings → Profile → Password on the web, or under Profile settings in the iPhone app.
Learn more: Managing your account and profile · How does Sign in with Apple work?