The best way to start in Vestibular Rehabilitation is to take the week long course at Emory University in Atlanta. It is run by Dr. Susan Herdman and leads to a certification in Vestibular Rehabilitation. In addition Dr. Herdman has written the best book available called "Vestibular Rehabilitation" that is now in the 3rd edition.
The course is by far the best continuing education experience you will have. The faculty is top notch, there is hands on practice with feedback for all important evaluation and treatment techniques. You will receive written instruction on everything learned.