To increase security on your user account, a 2-step verification process can be added. After normal log in, 2-Step verification will demand you to insert a code which Google will send you as a text message to the number you give them. You can activate 2-step verification with following instructions.
Activating 2-step Verification
1. Adding your phone number
- In Gmail, click your email address (or picture) and select Account OR go to address https://www.google.com/settings/personalinfo
- Choose security
- From 2-step Verification area, select Setup
- Select Start set up.
- Insert your phone number and click Send code
2. Confirm your phone number and the settings
- Enter the code you received in your phone and select Confirm
- Select Next (This setting doesn't apply when using SSO-service)
- Select Confirm