Two-Factor authentication allows you to have an additional layer of security to your account.
You have to have your phone number verified in order to use SMS 2FA, simply verify your phone number from the settings page (for more information on how to verify your phone number please click here)
To enable SMS 2FA simply tap the box near "Enable 2FA via SMS" on the "Settings" page. Then you will be asked to enter the one-time six-digit passcode that is sent to your phone.
When you get the code, enter it on the screen and tap "Enable 2FA". If you did not get the code on your mobile phone, please tap "I didn't receive the code". (You can resend the code once every 20 seconds). If you still do not receive the code please switch your phone off and on again.
Your account will now have 2FA enabled. Each time you log in you will be required to enter a one-time passcode sent to your phone.
To disable SMS 2FA, you need to go to "Settings" and tap the box near "Enable 2FA via SMS". You will then need to enter an OTP to disable this security feature.