A subagent is a private business who enters into contract with a County Auditor, and is appointed by the Department of Licensing Director to perform vehicle and vessel title and licensing services.
You may begin the process by contacting the County Auditor's office for the area where you want to do business. They'll be able to tell you if they're seeking an additional subagent.
For a list of all vehicle licensing offices and their contact information, see the list of vehicle licensing offices. The first listing under each county is the County Auditor's office.