The purpose of the USATF course certification program is to produce road race courses of accurately measured distances.
The easiest way to have your course certified is to hire someone who is already skilled at measuring courses for USATF certification.
Alternatively, you can measure it yourself if you are sufficiently motivated and willing to devote the time and attention that it requires. In either case, you may need to contact the USATF Road Course Certifier for your state. This person can refer you to qualified measurers that you might hire. Or, if you choose to measure the course yourself, the Certifier can provide guidance to help you through the process, and when you are finished, you will need to send paperwork to your state Certifier.
Because courses often degrade over time, all course certifications expire automatically 10 years after the year of issue, and must then be re-measured in order to be recertified.