How do I check the Primary claimed as a dependent box on the 1040?

 do you mean check? please clarify. 

If you can be claimed as someone else's dependent, then in MY INFO when it asks if someone else can claim you as a dependent, answer YES.

I'm not quite sure what you're asking! What do you mean by Primary?

However,

• Any dependent questions are in the My Info section of the tax return
• After you log into TurboTax, My Info is in the menu bar.
• If you've entered the information for yourself, and any others in your family, you can select their name.
• As you review the information you entered, one question is
  • Can someone else claim (you or them) as a dependent?
  • You can make any modifications in this area.

Please contact us again with any additional questions or to provide some additional details.