To sign up for the Credit Karma checking account, for the refund advance, you will need to be logged into TurboTax, have completed your tax return, and are ready to file.
Select File from the left menu (select the menu icon if you’re using the mobile app). When you reach Step 2 Your Refund Info, select Start. You’ll see Refund Advance as an option for receiving your refund. The Credit Karma Money Spend Account Only option does not include a Refund Advance.