I rec'd a 1042-S for a lottery winning in which the IRS kept 30% of the winnings for withholding tax. Where do I enter this information?

You can enter the tax paid on the Foreign Income page.

 

If you are using TurboTax Online, you can search for Foreign Income on the Tax Home page. 

 

If you are using TurboTax Desktop in EasyStep mode, select Income & Expense>T-Slips from the left side menu. Then you can check off the Foreign slip and then continue through the pages until you get there. 

 

If you are using TurboTax Desktop in Forms mode, you can search for the Foreign slip by clicking on the Forms icon in the blue icon bar.