Select Turn On to expand the Two-step verification section.You will be prompted to enter a phone number if you initially did not enter it during the set up of your account. Enter the number you want to use to verify the account and select Turn on text message verification.
Choose to receive the one-time pass code by either text message or voice message and select Turn On.
Enter the one-time pass code you received and select Continue.
To disable, follow the same steps except select Turn off after step 3.