How do I amend my tax return from this year?

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, Form 1040X, return 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.

On the Tax Home web page when the the Form 1040X for amending a 2019 tax return becomes available there will be a link - Amend (change) return

If you have filed your tax return and then discover that you have an error to correct you will have to wait until the IRS either accepts or rejects your tax return.

If the return is rejected you will correct the error that caused the rejection, and refile your return.  

If the return was accepted by the IRS then you will have to file an amended tax return using Form 1040X to correct the error to your tax return.

This link to the TurboTax Help page  How to amend (change or correct) a return you already filed provides information on how to amend your tax return.