To set two-factor authentication, go to your account settings section and select "Security".
Find the "Two-Factor authentication" section and click "Enable"
Before you enable the two-factor authentication, please save the backup code. In case of loss of the authenticator you will be able to recover the access only using this code.
Download and install the application for generating codes to your phone. Download the application using the links given here:
After you install the application open it and scan the QR code or enter the secret code:
Enter the code from the application and click the "Enable" :