As far as I know, a Form 1099-R from CalPERS is informationally no different than any other standard IRA Form 1099-R. Enter the Form 1099-R exactly as received under Wages & Income (or Personal Income) -> Retirement Plans and Social Security -> IRA, 401(k), Pension Plan Withdrawals (1099-R), then answer the follow-up questions. If the Form has code 3 in box 7, TurboTax will ask for the normal retirement age for the CalPERS plan and, if you were under that age, report the income on Form 1040 line 1 as wages rather than as pension income on line 4.
https://www.calpers.ca.gov/page/retirees/taxes/understanding-your-1099r-tax-form
