Did you follow the quick start instructions to set up the Authenticator first?
By default, unauthenticated users are redirected to the Sign In flow. You can explicitly redirect to Sign Up or Forgot Password:
Sign Up Attributes
The Authenticator automatically infers
but can be explicitly defined as seen below.
The Authenticator automatically renders most Cognito User Pools attributes,
with the exception of
zoneinfo. Because these are often app-specific, they can be customized via Sign Up fields.
By default, the Authenticator will still require any attributes required for
verification, such as
signUpAttributes is empty: