I forgot to file my taxes for 2019. All I have is a rrb-1099-r.

Yes?  You can still efile a 2019 return until Oct. 15, 2020.  

Go to Federal> Wages & Income>>Retirement Plans and Social Security  (SSA1099 and 1099RRB) to enter your SSA1099 or RRB1099

Careful though....the RRB-1099 and RRB-1099-R  are different forms.

1) The RRB-1099 goes in at  the same spot as an SSA-1099

2)  The RRB-1099-R  goes in with the other 1099-R forms, and when you start into that section, you will select the RRB-1099-R as a sub-selection.

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Don’t wait. File your taxes ASAP. Just follow the instructions in TurboTax.