You cannot change how you want to receive your refund after you file your tax return and it has been accepted.
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.
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