The current 2018 year is currently online and it can be efiled. https://turbotax.intuit.com/personal-taxes/online/
All prior year returns require the prior year tax program for each tax year and they must be paper filed. The 2015 return program will not be available after October 15th and unless you filed an extension for that year any refunds are void. https://turbotax.intuit.com/personal-taxes/past-years-products/
