How do I enter a U.S. donation to offset U.S. interest income on Turbo Tax.

Are you using TurboTax CD/Download or TurboTax Online?

I am using Online Turbo tax.  I have entered it in Donations but how do I get it to reduce my U.S. interest income?

In TurboTax Online, please do the following:

1. Use the Find tool 🔍 and enter “don” in the search bar.
2. Select “Donations Profile” from the search results, then click the Go button.
3. Check off “Donations made to the United States” and then click the Continue button.
4. On the U.S. Donations page, click the Add Donation for [NAME] button. Fill in the required information, then click the Continue button to save your changes. When you are finished entering receipts, click the Done with Donations button. 
5. On the United States Donations page, enter your eligible US income. Then click the Continue button until you get to the Donations Claimed and Carried Forward page. There you will see your US donation being claimed.

I am famliar with this but the donation is not lowering my U.S. income?  

I would like to know how does U'S donations lower your U.S. income???/. Where do I see this on my return?