Here is how to do it:
1- Sign in to your Google Account settings page by clicking on your name or picture in the upper right corner of the screen and then clicking Account.
2- On the left tab, click Security and then Edit under "2-Step verification." This will bring you to the 2-step verification settings page.
3- You will then see a step-by-step guide which will help you through the setup process.
4- Once you’re done, you’ll be taken to the 2-step verification settings page again. Be sure to review your settings and add backup phone numbers.
5- You’re done! Next time you sign in, you’ll receive an SMS with a verification code