2FA is not enabled on user accounts by default, and each user must enable it themselves. In order to do that, you must do the following:
On mobile:
Tap on the 
navigation menu in the lower-right corner of the screen and then tap on the
Settings menu option and choose [Two-factor authentication]
After that, tap on [Enable] and continue the setup flow
Note: Make sure you save your recovery code in a safe and easily accessible place. You may need it if you lose access to your 2FA codes.