Please take the following steps below.
1) Sign into TurboTax Online
2) Continue your return by click Taxes > Tax Timeline > Take me to my return.
3) Click on Federal Taxes tab (Personal depending on version)
4) Click on Other Tax Situations sub-tax
5) Scroll down to Other Return Info, Identity Protection Pin, click Start
6) Proceed through the interview to add you IP PIN
Please see the FAQ article below for additional information. https://ttlc.intuit.com/replies/3301088