How can I enter OP 1099-R ?

[HelenC12]

If you're referring to your SSA-1099-R-OP1 form, please see Where do I enter an SSA-1099, SSA-1099-SM, or SSA-1099-R-OP1?

Whether or not your Social Security income is taxable depends on your total income, including your Social Security plus any other income. Generally speaking, if your only income is Social Security, you probably don't make enough money to be required to file a federal tax return. 

To see if you have to file a tax return, see Do I need to file a federal return this year?

[SteamTrain]

Or are you talking about a CSA-1099-R from OPM ?

For that you enter it with the other 1099-R forms, but have to make sure you select the CSA- or CSF-1099-R form type during the setup questions in the 1099-R section.