How do I change estimated taxes after I have filed my return

If you mean that you want to pay a different amount of for estimated taxes for 2017, you can adjust your estimated tax payments for 2017 in TurboTax.

If you already filed your return and you used TurboTax Online, you can get back in to your return.

• Log in to your account.

• At the Welcome Home screen, go to the tab My TurboTax (see screenshot).

• Under Some Things You Can Do, at the bottom of the screen, Choose Add a State (you aren't really adding a State, but you will be able to access your return).  Take care not to make any changes to your tax return except for your estimated taxes.

Go to Federal Taxes, and choose Other Tax Situations.

Scroll down to Other Tax Forms, and start Form W-4 and Estimated Taxes.

Say that you don't want to change your W-4.

Say Prepare Now for estimated taxes.

On the screen Review Your Estimates for 2017, check that you want to adjust your estimates. Proceed to adjust your income estimates on the screens that follow.

If you don't want to do this in TurboTax, you can prepare 1040-ES vouchers by hand and either send them in with payment or pay electronically. 

https://www.irs.gov/pub/irs-pdf/f1040es.pdf 

https://www.irs.gov/payments/direct-pay