To find the Injured Spouse section in TurboTax, click on Federal Taxes, then Other Tax Situations, then scroll down and click on Other Tax Forms, and select Misc Tax Forms, and you'll see a list of forms to choose from. Click "Start" next to Report an injured or innocent spouse claim. Then follow the prompts.
Remember that you want injured spouse rather than "Innocent Spouse," since they're two distinct situations.
Also, here's a link to the TurboTax support page for injured spouse claims: https://ttlc.intuit.com/questions/1910698-how-do-i-file-form-8379-injured-spouse-allocation