homestead exemption question

How do I create a sworn and notarized affadavit? Would this task require a notary? I got a letter from the Harris County appraisal district after I had applied online for a homestead exemption a half year ago. I need to send a sworn and notarized affidavit stating the amount of square footage I occupy as your residence in the buildings. I live in a small MF building with 3 units.