To protect your account with two-factor authentication, please, do the following:
1) Download Google Athenticator app or a different app for the main platforms ssuch as iOS, Android, Windows Phone and Java:
In this example we will use Google Authenticator .
2) Create a key in the Security section of your profile on the website.
3) Activate Google Authenticator on your gadget and scan the *QR code.
4) After scanning the QR code Google Authenticator will generate one-time passwords every 30 seconds.
5) Enter your one-time password.
After that you will have to enter your one-time password every time you enter the account and (or) withdraw funds from your account.
Before confirming the creation of the key make a backup of the QR code or a key to avoid problems in case you have an issue with losing/rebooting your telephone. You should make a backup at an external storage such as a USB flash drive.
You can read more detailed information about two-factor authentication here: https://support.google.com/accounts/answer/1066447?hl=ru