If you have already filed your return, your bank account number cannot be changed unless the return is rejected. If you haven't filed your return yet, or if your return is rejected, you can change your bank information during the filing process. Click on the File tab and continue through the filing screens. TurboTax will bring you to the screen for entering your bank information.
If your return is accepted with the old account information, the IRS will try to deposit your refund into that account. If they are unsuccessful, they will mail you a check.
@bshep221990 The IRS does not allow you to change your banking information after you file your tax return. If you used a closed or incorrect account for your direct deposit, then the refund will be sent back and then the IRS will mail you a check, using the address you entered on your tax return.