Step 1

On Twitter, click on Settings and privacy, then go to Set up login verification as shown in the image below

Step 2

Click on Okay, send me a message then enter your password to verify it’s you.

Step 3

Next, enter the phone number you wish to use as the verifier (A code will be sent to the number almost immediately)

Step 4

Enter the code sent to you, and you are all set to start using 2-Factor Authentication on your account.

Now, when you (or anyone else tries to) login to your Twitter account, a six-digit code will be sent to your (verifier) phone number. Enter this code to successfully login.