If you have a smartphone download the Google Authenticator app.

Android:
https://play.google.com/store/apps/details?id=com.google.android.apps.authenticator2&feature=search_result#?t=W251bGwsMSwyLDEsImNvbS5nb29nbGUuYW5kcm9pZC5hcHBzLmF1dGhlbnRpY2F0b3IyIl0.

iPhone:
https://itunes.apple.com/us/app/google-authenticator/id388497605?mt=8