I filed with Turbo Tax for the first time last year. Previously I used an accountant. Long term capital gains (losses) were not included. How do I update the 2016 return

I had long term losses in the stock market through the years.  When I filed with TurboTax last year, this information was not included.  I did not have to pay taxes last year so a refund is not a problem.  I want the long term losses to be included in this years return 2017,

thank you