You will have to amend your previous year (s) tax return to do the carryback. You will see an option for this on your home page in TurboTax. You will also see an option to "save a copy" of your tax return to your computer, which will allow you to import your tax data from TurboTax online to your computer. It is in the "Tools" option if you are working on your current tax return, or in your history if working on a previous year.