You can enter your 1042-S related to your pension distribution and your related withholdings under the 1099-R section in TurboTax. You need to check the box for the option that "I need to prepare a substitute 1099-R" on the screen Tell Us Which 1099-R You Have. As it is a substitute1099-R (Form 4852), you will need to provide an explanation and mail your return along with your filing copy of the 1042-S,
You will find the 1099-R under Wages & Income, scrolling down to the section IRA, 401(k), Pension Plan Withdrawals (1099-R).
