I want to travel from Wuhan to Wudangshan by high speed train.

Well, there is no bullet train between these two places. Thus you can take the normal speed train from Wuchang Railway Station and get off at Wudangshan Railway Station. The train schedules are 05:35, 06:02, 08:29, 11:58 and 23:58. It takes 6-7 hours.
You can book the tickets when you arriving at the train station. But it's suggested to book it in advance in case of the tickets be sold out. TravelChinaGuide provides such online ticket booking service. If interested, their contact information is bookingtravelchinaguide.com.