I retired in Oct 2016 and received 3 pension checks.I entered all the info from the 1099R but turbotax asks for age and how much I paid on annuity start which i dont know

If you made contributions to a pension plan that were not deductible then a portion of the monthly payments each month is a return of your money and the rest is taxable.

If you paid nothing in, then you are correct, it does not change your taxable income.