If your business created a net operating loss (NOL) in a prior year, TurboTax would typically import that information into your current year return. If you didn't use TurboTax last year, you may enter the NOL information under Business Deductions and Credits.
Note that a business loss for a tax year does not always create a NOL. If you had other income to offset the loss, you may have already received a credit for the business loss on a prior year return. You may wish to consult with a tax professional in your area for advice specific to your tax situation.
The easiest way to find this topic in TurboTax Online is to go to the left column and click on Tax Tools >> Tools >> Topic Search. Type in "net operating loss", then click the topic in the list & Go to go directly to the start of that section.