How can I get back to my Federal form to change my deductions using Turbo Tax?

Try this: click on the Federal Taxes tab. From there, click on the Deduction & Credits link. When it asks if you want to go through everything or if you want to choose what you want to work on, select the "I will choose what I will work on" option. At the bottom of the page click on the Done with Deductions and Credits link. You will then see the page saying that based on the information you entered, you are getting the Standard/Itemized deduction of $$. Select Continue. You are now on the page where you can tell Turbo Tax to change your deduction method if it did not come up with the one you wanted.

We automatically select the deduction that gives you the best outcome on your federal taxes. Most 2021 federal tax filers will be better off with the standard deduction versus the itemized deduction.

In TurboTax, you can always switch to a different deduction. However, if you and your spouse are filing separate federal returns, both of you must take the same deduction per IRS rules.

Click this link for full instructions