Are you doing a 2020 return? Are you using the Desktop program installed your computer? Online is only good for 2021 now.
To enter withholding on Unemployment:
After you enter the Payer's name & address then on the next screen you select your state and enter the amount of Unemployment, there is a checkbox that says "Federal or state income tax was withheld on this payment". You have to check it for the withholding boxes to show up on the next screen.
For 2020 the federal income taxes withheld from the Form 1099-G will be included on the federal tax return, Form 1040 Line 25b.
Turbo Tax expert answer with screen shots of both Online and Desktop programs to enter withholding on unemployment
https://ttlc.intuit.com/community/retirement/discussion/the-1099-g-form-has-a-box-for-federal-income...
