This TurboTax website will let you register if you don't need to file: CORONAVIRUS TAX CENTER: 2020 STIMULUS
Just select: If you don’t need to file your taxes this year
If you are trying to enter this information while preparing your return, you will be asked for it when you reach the File portion of the preparation.
You will be asked several questions, need to sign authorization forms, and will then be asked how you would like your refund. You will be able to enter you banking information in this section.
On the personal info worksheet. Go to VIEW. Select FORMS. Select INFO WKS. Scroll to Part V. Hope that helps.
If you're entering your banking information before filing, you may not be asked for the bank's name. Entering the routing number identifies the bank to the IRS. Then you'll be asked to enter your account number. See the info linked below for entering banking information before completing your filing.
Where do I enter my bank's routing or account number?