I set up my return to be delivered via direct deposit however that account is no longer available. How can I change my direct deposit after already submitting my return?

You can't unless your efile rejects for something.  If the bank rejects the deposit the IRS will mail a check to the address on your return.

Thank you so much 

If your  tax return has already been accepted it is too late to change your bank information.  See this Turbo Tax FAQ regarding Entering the wrong direct deposit information.