Exempt interest dividends from mutual funds aren't taxable, but you should report them on your return if you're required to file. Dividends exempt from interest might be subject to Alternative Minimum Tax (AMT).
Since I am not seeing that you've specified US Govt Interest I am going to proceed with assuming that you do mean "Tax-Exempt Interest on Dividends".
Return to the section "Federal Taxes" - "Wages and Income" - select "I'll choose what I want to work on" and click on "Continue. Now, on the page titled "Your 2020 Income Summary", scroll down to the section titled "Interest and Dividends" and review the section for "Dividends" to be sure that you properly categorized the amount that is meant to be under exempt. You will see on that first screen after clicking "Start" or "Review" at the "Interest and Dividends" section that it states NOT to enter tax exempt interest on dividends here - so make sure this is not where you put this amount as it belongs in the "Interest" section and not the "Dividends" section. If this is what you've done, just continue to the end where you come to the page titled "Here's the Dividend Info we have so far" and delete the item from here by clicking on the trash can to the far right of that line item. It will ask you to verify that you wish to delete this form - select "Yes".
Now, go back to the "Your 2020 Income Summary" page and instead of selecting "Dividends", you will select "Interest" under the respective section. Once you get to the page titled "Let's get your 1099-INT or brokerage statement details", enter in the information for payor STOP, then CHECK THE BOX to the left of the statement below the payor information "My form has info in more than just box 1". You will now see a bunch of additional boxes - box #8 is where you will want to enter this amount.
