You have to supply PMI® with proof of the information you submitted in your application. For example, if you indicated you have a Bachelor’s degree in project management from Boston University, you’ll need to provide a copy of your transcript or diploma. You will need to verify your reported role and contributions to a project by having your project reference sign your printed description of your efforts.  You’ll gather everything and send the package to PMI®.  Most people report the audit process adds about 3 weeks to the application approval process; although I’ve had students complete it in less than a week.