Question

Where in Turbo Tax is the cost of my Federal Retirement Health Insurance entered?

If you paid health insurance premiums, include them as a medical expense on Schedule A.

Medical, dental, and vision expenses are reported on Schedule A and entered in the Deductions & Credits section.

With your return open, search for Schedule A and then select the Jump to link in the search results.
Answer Yes on the Did you spend more than $3,000 on medical expenses in 2020? screen.
Enter your medical expenses, starting with prescriptions, on the following screens.