Once you have submitted your return, you can not make changes to it unless it is rejected.
If the return is rejected, you can update the additional
information and correct the rejection, then submit the e-file again.
If the return was accepted by IRS, you will need to wait until it is completely processed and can then amend to make your changes. Amended returns are always filed by mail. You cannot e-file an amended return.
See the following answer to FAQ on how to amend or correct taxes you already filed. (TurboTax amendment program will not be available for a few more weeks.)
https://ttlc.intuit.com/replies/3288565
