There was a section on the federal tax return that asked my tax liability for 2017 and I entered the wrong amount. How do I get back to that section?

If you owe taxes on your return, the area which asks for your prior year tax liability is under the Other Tab in the federal interview on Underpayment Penalties line. Follow the questions until you reach the 2017 tax liability screen and correct your amount entered.

One of the exceptions for reducing or eliminating penalties for underpayment of taxes is calculated based on your 2017 total taxes on your prior year return.