You can go back to the beginning, where you entered "personal information" and change it. Head of household is basically a "single with dependent(s)." It's more or less the opposite of single with benefits 😉
You would have to go back to My Info and go back through the screens to see what you answered incorrectly that kept you from getting HOH----or maybe you do not meet the criteria to 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 MyInfo, and then enter your qualifying dependent, TurboTax will offer HOH as your filing status.