I am trying to sign into an account on Microsoft authenticator, but it asks me for the authenticator code to sign in, which I don't have because I'm not signed in yet. What do I do?

I am trying to attach a school email to authenticator but in order to attach, it asks me for the authenticator code, which I don't have because I'm not signed in yet. Seems contradictive to ask me to use the app that I can't use because I'm trying to sign in and it won't let me. There are no other options for alternative ways to sign in.