Thank you, Michael!
Follow Turbotax step by step, Turbotax is making me enter a 1099R. My option is either to import from my bank or brokerage or, type it in myself.
Turbotax then make me select one of four 1099R forms.
There is a check box for "I need to prepare a substitute 1099R", which will get you to form 4852.
Turbotax will only let you go to form 4852 after you have entered 1099R first.
That's why I was searching for what to do here, and I saw @macuser_22's post about how to enter a 1099r without actually having it.
