The IRS Website mentions an automatic 2 month extension for service members stationed abroad. How do I ensure this is on my return

It's not clear exactly what you mean by "the last year." You qualify for the automatic 2-month extension if you were stationed abroad on the original due date of your tax return, which was April 15. To get the extension, you have to include a statement with your tax return explaining how you meet the requirements for the extension.

You cannot create the required statement in TurboTax Online. If you use TurboTax Online you would have to create the statement outside of TurboTax, print your tax return, attach the statement, and file by mail.

If you use the CD/Download TurboTax software you can create the statement in TurboTax and include it in an e-filed tax return.

Note that if you are getting a refund there is no penalty for filing late, so you don't really need the extension. If you owe tax, the extension eliminates the penalties for late filing and late payment, but you will still be charged interest from April 15.