You will find the line of questions that determine your filing status under the My Info section (Personal Info). Click on that tab (left hand of the screen if using TurboTax Online) and you will get to the Personal Info Review page. There will be an edit option (looks like a pencil) next to your name and your dependents name. Depending on why you were determined not eligible the first time around, you will have to edit and go back to the questions. There is not going to be one single question option for you to switch to Head of Household - you have to answer the questions appropriately to get the status.