How do I file an extension for oklahoma state tax when my federal has been accepted

There is nothing you need to file.

Oklahoma automatically gives you a 6-month extension to October 15 if you filed a federal extension and have paid or withheld at least 90% of your total Oklahoma tax liability. Otherwise, mail Form 504 by April 15. If you owe 10% or more of your total tax liability, submit payment by April 15 to avoid penalties by including a check with Form 504.