You won't be able to make any changes until your return has been accepted or rejected by the IRS. If rejected, you would need to correct any information that caused your return to be rejected as well as make any other changes to your return that you see fit, then proceed to resubmit your return. If accepted, you would need to amend your return. See the link below for instructions on how to amend.
https://ttlc.intuit.com/community/amending/help/how-do-i-amend-my-turbotax-online-return/00/27577