I amended my 2019 federal tax return & chose to apply my refund to my 2021 estimated tax. Where do I enter that in TurboTax 2020 to affect 2021 estimated tax vouchers?

Earlier today I found how to apply it to my 2020 tax due but then remembered that on the 1040-X I said I want it applied to 2021 estimated taxes.  Now I can't find where I entered it for 2020 to remove it.