The Office 365 Admin connector is authenticated and authorized using Oauth2. When you add an Office 365 Admin card to a Flow for the first time, you'll be prompted to create a connection.
You must be an Office 365 administrator in order to authenticate with this connector.
You can create multiple connections and manage them from your Connections page.
To create a new connection from an Action card:
Click New Connection.
Add a Connection Nickname. This is useful if you plan to create multiple connections to share with your team.
When the Oauth window pops up, log in with your Office 365 administrator account and continue.