If you did not complete form 8379 to e-file with TurboTax, you can manually fill out the form and mail it to the IRS. Please click on the link below to be taken to a PDF of Form 8379. If you save this to your computer and open with Adobe Reader you will be able to complete the form on your computer, sign, and mail to the IRS.
Form: https://www.irs.gov/pub/irs-pdf/f8379.pdf
Instructions: https://www.irs.gov/pub/irs-pdf/i8379.pdf