Be VERY sure you do not change anything on the actual return ... ONLY work in the estimated section so you don't adulterate the filed return.
To open the return once you have filed log in and scroll down and click on ADD A STATE ...

Can TurboTax calculate next year's federal estimated taxes?
When you prepare your 2018 return, we'll automatically calculate your 2019 estimated tax payments and prepare 1040-ES vouchers if we think you may be at risk for an underpayment penalty next year.
You can also calculate your 2019 estimated taxes and generate the payment vouchers by doing this:
- With your tax return open, search for 1040-es(be sure to include the dash) and select the “Jump to” link.
- Answer No to the question Do you want to change your W-4 withholdings for 2019?
- On the next screen, Review Your Estimates, select Review Now. Answer the questions about things like your 2019 filing status, income, and deductions.
- Eventually, you'll come to the Print Vouchers? Answer Yes and we'll include your 2019 1040-ES payment vouchers when you print a copy of your return later.
Rest assured that TurboTax uses the most recent tax rates when calculating your 2019 estimated taxes.
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