@rsmith2134 , while I am not familiar with the screens of the on-line TurboTax product(s), if the IRS letter is asking you to file a Schedule-SE, you can always download the form at www.IRS.gov. It has both the form and the instructions in .pdf format. Thus you can print, fill by hand and mail in the form along with any amounts due.
To help you , you need to tell more about your income source. Is your income from sole-proprietorship / self-employment ( both of which would have a schedule-C in your tax return and should have created a Schedule-SE ) ? Or are an employee of an international institution or foreign embassy/consulate ?
Please answer my questions so one of us can help you fill the request from IRS --yes ?