If you want to secure your Facebook account then try this method
How to activate Two-Factor Authentication
1) First of all log in to your Facebook account.
2) Click on the triangle visible on the top right and go to Settings.
3) After going to Settings, you will see the option of Security and Login on the left side.
4) After clicking on Security and Login, you will find Change Password and Login options at the bottom. Just below these options is ‘Two-factor authentication’.

5) Click on Two-Factor Authentication.

6) After this click on Get Started.

7) Now you will have two options – text message and authentication app.
The first method is Text Message
1) If you choose the text message option, you will have to enter a phone number. Keep in mind that a code will be sent to this number for verification.

2) After entering the number you will receive a code on your phone.
3) Two-factor authentication will be activated once you enter the code.
Second method: Authentication App
1) If you do not want to enter your mobile number then you can select this option. For this you have to download the Google Authenticator app visible on the screen.
2) After downloading the app, scan the QR code appearing on the screen with the help of authentication app.
3) After this enter the code shown in the app on the computer.
4) After entering the code, you will see that two-factor authentication will be turned on.