You cannot amend to change banking information.

Did you already e-file?  If you did NOT e-file you can go to the FILE section and change how you want to receive your refund.  If you want direct deposit you need the routing number and your own account number.

You cannot  change banking information while your return is in pending, nor can you change it after the return is accepted.  The IRS does not allow it.

If you e-filed:

Banking information for direct deposit is wrong

If you entered incorrect banking information for your refund, you can change it if your return is rejected.  If it is accepted, however, it is too late to change it.  The bank will reject the refund and send it back to the IRS.  Then the IRS will issue a paper check and mail it to the address you put on your tax return.  Expect a delay of at least a couple of weeks to receive your refund.

Here is what the IRS says about entering incorrect banking information

https://www.irs.gov/help-resources/tools-faqs/faqs-for-individuals/frequently-asked-tax-questions-answers/irs-procedures/refund-inquiries/refund-inquiries-18

If you filed the original return with the wrong bank info you can not fix that.  If the bank rejects the deposit the IRS will mail a check to the address on your return.  You can't amend for that.  Did you need to amend for something else too?

You can't amend your return to change banking information.  Unfortunately, if your return has been accepted, you cannot change your banking info.  See the following for more information: 

What if I entered the wrong bank account for direct deposit?

https://ttlc.intuit.com/community/refunds/help/what-if-i-entered-the-wrong-bank-account-for-direct-deposit/00/26213