Steps to enable for the 2-Step verification:
1. In your Gmail account visit the "Signing in & security" and click "Security Checkup".
2. You will be directed to the login web page. Log in using your username and also password.
3. On the right you will see the 2-step verification box, select "Start Setup".
4. After that just adhere to the step by step experience to enable the 2-step verification.
Steps to disable the 2-Step Verification:
1. In your Gmail account visit "Signing in & security". You will be guided to the login home window. Here, visit with your username as well as password (and also verification code if asked).
2. Click on 2-Step Verification on the right.
3. Click "Turn off 2-Step verification".
4. You will be confirmed once you have disabled the 2-Step verification. Click "Ok".