Go to Deductions & Credits -> Retirement and Investments -> Traditional and Roth IRA Contributions. Proceed through the questions until TurboTax asks you to confirm the amount of excess contributions carried in from 2015, then replace the amount shown with a zero.
Otherwise, clear and start over on your 2016 tax return after amending your 2015 tax return and uploading your amended TurboTax tax file.
