You do not amend a tax return to add a Form 8379, Injured Spouse Allocation. Click on Cancel Amend on the left side of the screen.
See this TurboTax support FAQ for the Form 8379 and how to complete the form after the 2019 tax return has already been filed - https://ttlc.intuit.com/community/accessing/help/how-do-i-file-form-8379-injured-spouse-allocation/0...
