Two Factors Authenticator:

 

 

There are two apps to choose, the Google one is simple and straight forward while the Microsoft one is more complicated but more secure as it need you to verify every time you use it. The 6 digit code will change every 30 seconds and it doesn't follow the time you start using the app, so it will be better to wait for it to refresh as it will give you more time to type in the code.

Just need to log in to your account and select security under account and choose the Two Factors Authentication, you will be prompt to enter your password and date of birth before you can generate a QR Code for your phone app to scan. It will automatically save your account details in the app for easy access, and you can see the change of 6 digits code every 30 seconds.

It will log you out of your account and prompt you to log in again with Two Factors Authentication again to verify, and your account will remain log in from then onward. I had try out my 6 accounts with 3 on Google App and 3 on Microsoft App, so far I still like the Google one better. But for those who want more security and doesn't mind the additional hassle of having to verify again every time you use the app the Microsoft one will be a better choice. There are many other similar app which does the same but I decided to choose the more recognize one.