You asked a similar question in another thread. If you have already e-filed and the IRS accepted your return, the IRS does not allow you to change how you want your refund and switch to direct deposit. They do not let you change from a mailed check to direct deposit. You can, however, send a correct mailing address for them to mail your check to; if you do not send in a change of address, they will use the address you entered on your tax return.
https://www.irs.gov/faqs/irs-procedures/address-changes/address-changes