You have to go through the USAA portal to receive the discount. Also the discount is up to $20 and depends on what product you are using. I will also post other discount information below.
If you have Family income $64k or less in 2016: You may be able to file for free using our Tax Freedom Edition: https://turbotax.intuit.com/taxfreedom/
If you do not meet the requirements above here are our other discounts: https://turbotax.intuit.com/personal-taxes/online/military-edition.jsp