If you have not already e-filed your tax return you can see the following TurboTax FAQ for information on how to get to the area of your return to enter/change your bank account information.
https://ttlc.intuit.com/replies/4083015
If you have already filed your tax return, you cannot make any changes as to how your refund will be paid. The IRS rules state that taxpayers cannot rescind a Direct Deposit election and they cannot make changes to routing transit numbers of financial institutions or to their account numbers after the IRS has accepted the return. Refunds that are not direct deposited because of institutional refusal, erroneous account or routing transit numbers, closed accounts, bank mergers or any other reason are issued as paper checks, resulting in refund delays of up to ten weeks.