In your open return (TurboTax Deluxe Windows) switch to forms mode by clicking on View and selecting Forms. Click on Open Form. Type 4852 in the search box then select the Form 4852 form and click Open Form button. Follow the directions at the top of the page for entering the 1099 R information. See screenshot below.
Did not have this problem last year... I receive a pension from an intergovernmental organization that does not use 1099-R. When you pull up the TT version of 4852, it demands "zooming" into Personal & Income Worksheets first before entering in the actual 4852, in my case, clicking on the check-box for the 1099-R linked form. But when I try to input my name and SSN, the employer's name and address, etc., in either the Worksheet or the TT version of 4852, it highlights the fields and won't take the inputs and keeps referring me back to the Worksheet that doesn't work, either.
To use Form 4852 to prepare a substitute Form 1099-R, you go through the Form 1099-R section itself. Choose to type in the information for the Form 1099-R instead of trying to import it. Then, check the box showing you need to prepare a substitute Form 1099-R and follow the instructions on the screen.
See the picture below for a visual reference: