If you have already filed then you will need to file an amended return.
If you have not filed you tax then you can just revisit the 1099-R section and add the additional information.
What if you've sent in your income tax return and then discover you made a mistake? You can make things right by filing an amended tax return using Form 1040X. You can make changes to a tax return to capture a tax break you missed the first time around or to correct an error that might increase your tax.
-follow these links for more information-
Video: How to Amend Taxes that Are Already Filed - TurboTax ...
Where do I enter my 1099-R? - TurboTax Support
