The Federal Carryover Worksheet is populated automatically from your prior year return (if available) and your manual entries to carryover questions on the Step-by-Step interview pages. Look for questions about Passive Loss Carryovers from rental properties, Capital Losses from sales of investments, Section 179 carryovers for your depreciated assets or on Schedule K-1, the home office deduction, or a Net Operating Loss, among others.
If you're using TurboTax for Desktop, you can use Forms Mode to open the Carryover Wks form and manually enter the amounts. Any box highlighted in yellow will accept manual entries. When you reach a number in blue, you can revise that number without creating a form error. Any form with a red exclamation point has an error. Click the Errors icon above the forms list to see an explanation of that error below the form when opened in the large window. Any number in green was imported from last year and should not be changed.