Be careful of where you enter the forms.
Ther are two possible forms.....in two separate menu item areas.
1) an RRB-1099-R goes in where you enter the regular 1099-R forms. When you start into that area to type in the data manually, you will be given 4 choices, one of which is an RRB-1099-R
2) The other possible form is the RRB-1099 (but no trailing "-R"). that goes in where you enter the Social Security SSA-1099, and when you get into that Q&A there is a checkbox to indicate it is the RRB-1099 version.
Your RRB-1099-R is entered in the same section as other Forms 1099-R.
As noted by @SteamTrain, RRB benefits payments are reported on one of two forms, depending on the type of payment:
To enter your RRB-1099:
To enter your RRB-1099-R (green form):
To enter your RRB-1099-R:
See this TurboTax help article and this one for more information.