When you are in your federal return, to go to the section in TurboTax where your federal estimated tax is calculated, please follow these steps:
Since you have already filed your return, you can use Form 1040-ES, to figure estimated tax.
To figure your estimated tax, you must figure your expected adjusted gross income, taxable income, taxes, deductions, and credits for the year. When figuring your estimated tax for the current year, it may be helpful to use your income, deductions, and credits for 2020 as a starting point.
There is a worksheet in Form 1040-ES that will help you figure your estimated tax. You need to estimate the amount of income you expect to earn for the year. If you estimated your earnings too high, simply complete another Form 1040-ES worksheet to refigure your estimated tax for the next quarter. If you estimated your earnings too low, again complete another Form 1040-ES worksheet to recalculate your estimated tax for the next quarter. You want to estimate your income as accurately as you can to avoid penalties.