Was this a direct trustee-to-trustee transfer where the funds were never paid to you personally? If so, the transaction is not a rollover and is not reportable on your tax return. It's only a rollover if the funds were paid to you and the distribution from the original HSA was reported on a Form 1099-SA.
If you received a Form 1099-SA because the distribution was paid to you, answer Yes when asked if you used the HSA to pay for anything, enter the details of the Form 1099-SA, indicate that you did not use all of the money for medical expenses, then indicate the amount used for medical expenses and the amount rolled over. TurboTax will include on Form 8889 line 14b the amount of this distribution that you rolled over.
