If you have not filed yet, then go back through the interview to file your return (File tab). When you get to the screen where it asks about your refund, choose direct deposit, you can change it there.
If you already filed your return you will have to wait until you get the status of your return (accepted or rejected).
If it gets accepted you will not be able to change it, if your banking information is wrong, then your refund will automatically be switched to receiving a check once your bank rejects the direct deposit.
If your return gets rejected, you can correct your account information, and then re-e-file
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What if I entered the wrong bank account for direct deposit?
