Since the forms and tax brackets change from year to year, you will need to use the 2015 TurboTax software to file your 2015 return.
Note: All returns for years prior to 2016 will need to be paper filed, as taxing authorities do not accept efiled returns after the extended due date (October 15, 2016, for 2015 returns)
TurboTax software for 2015 can be found at https://turbotax.intuit.com/personal-taxes/past-years-products/
