Two-factor authentication secures your account by requiring a validation code sent via SMS when you log in to ZapSign.
To activate it:
1) Click on your email in the upper right corner of the screen and go to "My Profile".
2) Scroll down to "Two-Factor Authentication" and click the "enable 2FA" button.
3) As soon as you receive the code on your phone, paste it in the requested field and click "activate code".
Once this is done, in addition to your email and password, you will always be asked to log in with a code sent to your SMS.