Because you were over age 59½ and the Roth IRA had been at the custodian only since 2017, you should have code T in box 7 of the Form 1099-R.
Enter the code T 2018 Form 1099-R exactly as received under Wages & Income (or Personal Income) -> Retirement Plans and Social Security -> IRA, 401(k), Pension Plan Withdrawals (1099-R). Click the Continue button on the Your 1099-R Entries page and in the questions that follow indicate that you had a Roth IRA before 2014. TurboTax will the treat the distribution as nontaxable by including the distribution on Form 1040 line 4a but excluding it from line 4b. No Form 8606 Part III will be included with your tax return.
Ignore any TurboTax income summary pages, they are more confusing than helpful. Look at Form 1040 instead.
