Open Gmail and go to your account settings.
Video Upload By Google : https://www.youtube.com/watch?v=zMabEyrtPRg
Suggested by http://www.tophotlines.com/gmail-customer-service
Then go to security. On 2-Step verification click "Settings".
Click "Start Setup".
You'll get a text-message on your cellphone with a code. Enter the code.
Click "Next".
Click "Confirm".
Click "Do this later."
Next to "Mobile application" select Android or iPhone.
Gmail will show you a QRCode.
Open the Authy App and on the sidebar click the "+ Authenticator Account". Click "Scan QR Code" and use your camera to scan it.
Enter the "Token" that you see in the screen on "Code:", then click "Verify and Save". You're done.
Video Upload By Google : https://www.youtube.com/watch?v=zMabEyrtPRg
Suggested by http://www.tophotlines.com/gmail-customer-service