If you do not have any Capital Gains this year to apply your losses to, you can "carry them back" three years, or forward indefinitely.
After you enter your Capital Gains details in to TurboTax, and a loss is calculated, you will be prompted in the Review section to carry them back or forward. (In paid versions of TurboTax, you can access the screen by searching for "loss"). If you choose to carry them forward, when you receive your NOA, it will state on there how much you have for Net Capital Losses to apply in future years.
