Office 365 Microsoft Authenticator setup

.. Two weeks ago, I setup Office 365 with 4 domains.
I have all the login passwords etc,

Since setting up 365, each day when I login I see a message counting down the number of days, before I need to setup Authenticator and two step verification. And now, my final day has passed and I currently I cannot login without the Authenticator App setup.... So, I need help to setup Microsoft Authenticator, to enable me to login to each of my domains. I've tried to do it, but Authenticator is telling me I'm using the wrong passwords, which I'm not.

Thank you