Go to the Autodesk Community. Answer 5-10 beginner questions per week. Don't be a bot—be genuinely helpful.
After ~100 quality answers, you'll get noticed by moderators. They will invite you to the "Expert Elite" program. There is no application form. They find you.
Think of it like a black belt in karate. You don't download a black belt; you earn it through thousands of hours of practice and helping others.