Here's how to prepare an injured spouse form (Form 8379) in TurboTax Online.
Click the Search button at the top and enter "injured spouse" (without the quotes) in the search box. Then click the link that says "Jump to injured spouse." This will take you to a screen that asks if you want to claim innocent or injured spouse relief. Click Yes.
Read the screens carefully. You want injured spouse relief, not innocent spouse relief. You will first get two screens for innocent spouse relief. Just click Continue without entering anything. Then you will get a series of screens for injured spouse relief.
You didn't say whether you are filing the injured spouse form for 2018 or for an earlier year, and whether you have already filed your 2018 tax return. If it's for 2018 and you have not yet filed the tax return, you can include the injured spouse form with your tax return. Otherwise you can file it separately. One of the screens will ask you whether you want to file the injured spouse claim with your 2018 tax return. If you select Yes the form will be included in your return. If you select No, after you finish entering the injured spouse information there will be a button to print Form 8379 so that you can mail it. You cannot e-file Form 8379 separately from your tax return.
If you are filing Form 8379 by itself, note the following from the IRS instructions for Form 8379.
"If you file Form 8379 separately, please be sure to attach a copy of all Forms W-2 and W-2G for both spouses, and any Forms 1099 showing federal income tax withholding, to Form 8379. The processing of Form 8379 may be delayed if these forms are not attached, if the form is incomplete when filed, or if you attach a copy of your joint tax return."
The IRS instructions for Form 8379 may be helpful. You can download them from the following link.
https://www.irs.gov/pub/irs-pdf/i8379.pdf
