If you've already filed and your return has been accepted, you will have to mail Form 8379 to the IRS using TurboTax to create the form.
Using TurboTax Online, open your return and sign in. On the Welcome home screen, select Taxes. On the Tax Timeline screen, select Amend (change) return.
When your return is open, In the search box, search for injured spouse and then click the "Jump to" link in the search results. Answer Yes to Do you want to claim innocent or injured spouse relief? and carefully follow the onscreen instructions for Injured Spouse.
Please see the following TurboTax FAQ, "How do I file Form 8379, Injured Spouse Allocation?:
Form 8379 lets the "injured spouse" get back his or her portion of a jointly-filed refund, if it's seized or offset to pay the spouse's debt.
Please also see the following IRS Tax Tip, "Injured or Innocent Spouse Tax Relief":