How to protect your data by making Gmail as secure as possible?

There go to the account security options. Once you click the account security find the opting which prompts you to add your phone number to the account as a security measures. Once you have registered the phone number, if there is any attempt to violate your account from another IP address other than the one you have registered as your own, the access would be promptly blocked and you would be send an alert regarding the same.