If you filed your tax return--and it was accepted -- using the wrong filing status, then you need to wait until it has been fully processed, and then you can amend it to change your filing status to Head of Household IF you qualify as HOH. However, if you entered your dependents and answered the questions correctly when you prepared the return, it should have offered you the status of HOH. Are you sure you can file as HOH?
Am I Head of Household?
If you qualify as Head of Household, when you enter your filing status (single or married filing separately) into Personal Info, and then enter your qualifying dependent, TurboTax will offer HOH as your filing status.
If you do need to amend, wait until the system is switched over fully from the 2018 to 2019 software sometime in December.
A 1040X cannot be e-filed. It must be printed and mailed. It will take about 3-4 months for the IRS to process an amended return. It is a good idea to use a mailing service that will track it, like UPS or certified mail, so you will know it was received.
Wait about 3 weeks from mailing and you can check the status of your amended return: