If you mean that you owed federal tax due for your 2017 tax return, then if you are getting a refund for your 2018 return, the IRS will offset that 2018 refund for the tax you still owe. You do not have to enter anything on your 2018 return about that; the IRS will take care of it automatically and send you a letter afterward.
But do understand that TurboTax does not know that you did not pay 2017 tax due. The results of your 2018 tax return do not include anything about the tax you owe from 2017. Your 2018 return only shows your refund or tax due for 2018.