Need to Amend a Federal Return

Once a tax return has been e-filed it cannot be canceled, retrieved or changed.
If you have e-filed your tax return and need to change, add or delete information on the tax return then you will need to wait for the tax return to either be accepted or rejected by the IRS.
If the tax return is rejected then you can make your changes and re-file the tax return.
If the tax return is accepted then you will have to amend the tax return to make your changes. An amended tax return, Form 1040X, can only be printed, signed, dated and mailed by you to the IRS, it cannot be e-filed. The IRS will take up to 4 months to process the amended tax return. Wait until you have received the tax refund or the taxes owed have been paid and processed by the IRS before amending the tax return.

To access your online tax returns sign onto the TurboTax website with the User ID you used to create the account - https://myturbotax.intuit.com/

Scroll down to the bottom of the screen and on the section Your tax returns & documents click on Show. Click on the Year and Click on Amend (change) return

See this TurvrboTax support FAQ for amending a 2019 tax return - https://ttlc.intuit.com/community/tax-topics/help/how-do-i-amend-a-2019-return-in-turbotax/01/1238456#M4600