If your 2017 tax return already reflects the Roth IRA contribution that resulted from the recharacterization, i.e., there is no deduction for a traditional IRA contribution and no Form 8606, there is nothing you need to do. You can enter the code 2018 Form 1099-R into 2018 TurboTax, but TurboTax will ignore it other than to remind you that the recharacterization applied to your 2017 tax return.
