In your case, the answer is: you don't.
However, again in your case, it won't matter, because of penalty for carryover over an excess contribution is 6% of the lesser of the carryover or the value of your HSA at the end of the year. Yes, because the value of your HSA was presumably zero at the end of the year, your penalty is 6% of zero, which is zero.
And since you are on Medicare, you will never be able to contribute to an HSA again, which means that the value of your HSA will never be anything other than zero.
So, while you do have an excess contribution to carryover, you have no way to pay it off but no penalty for not paying it off.
in 2017, TurboTax will report your excess contributions as taxable income. If by some chance, the value of your HSA was not zero by December 31, 2017, you will have some small penalty to pay, but since the fair market value of the HSA is now zero, for every year to come, the penalty will be zero.
I imagine that you made distributions out of that money that you contributed when you weren't eligible - you will need to contact the HSA administrator and try to return the "mistaken distributions".
