Form 1098 is for mortgage interest expense. To enter in TurboTax, follow these steps:
From the left menu, select Federal
Select Deductions & Credits, the second tab from the left across the top
Scroll down to all tax breaks and find Your Home. Click Show More
Select Mortgage Interest and Refinancing (Form 1098) and click Start
Mortgage interest expense is reported as an itemized deduction. TurboTax will automatically determine if you should use the itemized deduction or standard deduction.