How do I manually add prize winnings if I didn't receive a 1040-misc?

I would report as "Other Income".  To do so, while logged in to your return:

• Click on Federal
• Click on Income & Expenses
• Scroll to the bottom of the "Your income and expenses" page, and click on "Less Common Income" 
• Click on "Show more"
• At the bottom of the page, next to "Miscellaneous Income..." click on Start/Revisit
• Other reportable income - click on Start, then answer Yes 
• Give a description and enter amount of income from the prize winnings

This amount will also be reported on line 8 of Schedule 1 (Form)

Thank you, that worked great.