In 2018 TurboTax, enter the original Roth IRA contribution under Deductions & Credits. In the follow-up, indicate that you "switched or 'recharacterized'" the contribution to be a traditional IRA contribution instead and that the amount of contribution that you recharacterized was $5,500. TurboTax will prompt you to enter an explanation statement describing the recharacterization where you'll indicate that you recharacterized your entire $5,500 and an adjusted amount of [whatever the amount was] was transferred to the traditional IRA. TurboTax will then treat this $5,500 contribution as either a deductible or nondeductible traditional IRA contribution depending on your eligibility for a deduction (or your election to make it nondeductible if otherwise deductible).
Separately, enter the code N 2018 Form 1099-R that you'll be receiving that reports the recharacterization.
Finally, enter the code 2 2018 Form 1099-R that you'll receive that reports the Roth conversion. Assuming it's the case, indicate that the entire amount was converted to a Roth IRA.
Be sure to click the Continue button on the Your 1099-R Entries page and answer the additional follow-up questions, particularly the one that asks for your December 31, 2018 balance in traditional IRAs. TurboTax will prepare Form 8606 to calculate the taxable amount of the Roth conversion.
