My return is ready to be efiled but I need to add Form 9465 for extension of time to pay tax due. How do I add that form to Turbo Tax and file my return by efile?

Yes, Form 9465, Installment Agreement Request, is available as a payment option in TurboTax. 

If you are completely done with your tax return, continue into the File section. When you get to Step 2, you will see it as an option for payment of your taxes.

Follow this link to learn more.