If you are trying to add an additional 1099R from a different Institution than the one you have already added, here are the instructions:
1. Go to Federal.
2. Select Wages and Income.
3. Go to the Retirement Income section where you've already added a 1099-R.
4. You will see a box to add another 1099-R on the bottom left of your screen.
5. Once you have chosen that area, you can add the additional 1099-R.