You can chose which authentication method to use from this ones, as long as the method has been registered first. For better security we recommend that you use the method via the Authenticator App.

Below the instructions how to add this method and selected as default

Step 1: go to myMFA.ef.com, you will be required to use your second authentication first for security. Click in "Add Method"

Select Authenticator app

Step 2: When you get the below window, you need to download the "Microsoft Authenticator" app from either apple store or play store on your phone.

Step 3: after scanning the QR a notification will be sent to your app, "Approve it"

Step 4: Set up the authenticator app as default authentication method

Click on Change next to default sign in method and select "Microsoft Authenticator - notification" and confirm

You will receive a message in the website that your default authentication method has been changed.

From now on, time to time when you try to login in your account, you will be asked to authenticate by a code sent to your app (Authenticator) on your phone.