If data for State Employees Credit Union, an IRA, is data for Office of Personnel Management Retirement Operations, pension, can it be corrected?

What are you trying to correct? Did you enter IRA data as if it were a pension or vice-versa?

In any case, it sounds like you need to delete whatever it is you entered and enter the correct item instead. 

Go to Wages & Income-> Retirement Plans and Social Security->IRA, 401(k), Pension Plan Withdrawals (or some variation of this), press Start or Update, then delete the bad entry off the table, and then enter the correct one.