To the extent that your foreign Social Security payments are taxable income for United States purposes, then you should use distribution Code 7 (normal distribution) as your choice here. That will tell TurboTax to tax your foreign pension payments as ordinary, taxable, income. You can use this code if you follow the reporting method outlined under the Form 4852 (Substitute for 1099-R) data entry.
A different, alternative choice, would be to forego using Form 4852, and to declare your foreign pension instead as "other income" directly on Form 1040, Line 21. Regardless of which method you chose, however, the end tax result is the same.
I discuss the tax treatment of foreign pensions in somewhat more detail at the following TurboTax AnswerXchange link:
https://ttlc.intuit.com/questions/3767877
But the answer to your original question, and they way to resolve your current issue in the software -- assuming that you didn't repay any of your foreign pension benefits, or didn't have another "unusual" event or experience regarding them -- will be to use Code 7 (normal) for the Form 4852 8(j) entry.
Thank you for asking this question.
