I got a denial letter and it said I needed to send in a 7072 form how do I fill it out?

There is no such IRS Form 7072.

If you meant IRS Form 7202, Credits for Sick Leave and Family Leave for Certain Self-Employed Individuals, then go to this IRS website for the Form and Instructions for tax year 2021 - https://www.irs.gov/forms-pubs/about-form-7202

If you purchased Audit Defense for your  tax return, call TaxResources, Inc. at 877-829-9695, or report your IRS letter on their web site. http://intuit.taxaudit.com/ Do not contact the IRS until you have spoken to TaxResources. They may contact the IRS on your behalf.

If you did not purchase Audit Defense, you can get help with your IRS letter from TurboTax at the following link.

We can help you with your IRS letter

Was there a 7202 in your return and did you fail to mail it in with the original 1040?  If so save a PDF of the return now and see if you can find that form already filled in and send it as requested.