Get your taxes done using TurboTax

To add a dependent, you need to go to the Personal Info section in TurboTax and edit your name under Your Personal Info Summary.  

Work through that section and you will come to a screen that says Do You Have Children or Financially Support Another Person?, to which you have to answer "Yes". 

On the next screen you can indicate that you support your child or another person and then on the next screen you can enter the name and other required information for your dependent.