If you're getting a refund, we'll ask for your bank account info once you choose the direct deposit option (it's on the How Do You Want Your Federal Refund? screen in the File section).
If you owe additional taxes to the IRS and you're e-filing, enter your bank account info on the How Do You Want To Pay Your Federal Taxes? screen (choose the first option, direct debit). Direct debit is not an option for paper-filed federal returns.
To review previously-entered bank account info, simply revisit the File section in TurboTax and step through the screens.