Enter your Roth contribution when completing your return. TurboTax will state that you were not eligible to make a Roth contribution and ask what you plan to do to correct this. Select the option that says the excess contribution was removed before the due date of the return.
Since you made the contribution to your Roth IRA in 2018 (between January 1, 2018 and April 15, 2018), but you designated it as a 2017 contribution, and you withdrew it in 2018, the distribution form you get will be for 2018. Include the Form 1099-R on your 2018 return. Your Form 1099-R will have a code 8 and a code J in box 7.
See the TurboTax FAQ below for steps on entering your Roth information in TurboTax. Click "See entire answer" for the full page view.