To enter the withholding from your IRA distribution, follow the steps below.  It should be in Box 4 of your 1099-R. 

• Type 1099-R in the search box and click search.
• Click on Jump to 1099-R.
• If you have already entered or imported your 1099-R, on the screen Choose your bank or brokerage, scroll to the bottom and click on I'll type it in myself
• You can import it if you have not already entered it. It should import the withholding in box 4 as well as the other information
• Continue with the onscreen interview.
• On the screen Enter your 1099-R, type the withholding in Box 4 Federal Income Tax Withheld