@dingsl - you can  with an amendment.  That means there is a dependent that you didn't claim that you are now going to claim.  What are the circumstances? did this person live with you for more than 6 months? did you provide more than 50% of the expenses to run the household.  Did this person earn less than $4300? Tell me more please, let's make sure you can claim this person.. 

Am I Head of Household?

https://ttlc.intuit.com/questions/1894553-do-i-qualify-for-head-of-household

https://ttlc.intuit.com/questions/2900097-what-is-a-qualifying-person-for-head-of-household

If you qualify as Head of Household, when you enter your marital status (single or married filing separately) into MyInfo, and then enter your qualifying dependent, TurboTax will offer HOH as your filing status.

You are asking from TT Live, so please contact your Live rep.