We will arrive by train to Huaihua at 6:20am and we want go to Fenghuang by bus.

Nadia, do you mean the Main Railway Station or the South Railway Station?
If it's the Main Station, you need to take bus no.17 for 3 stops to the Huaihua West Bus Station first. Then you can take a shuttle bus to FH North Bus Station at the cost of CNY39/person.The bus operate time is during 06:40 to 17:40. The interval is 0.5-1.5hrs. Upon arrival, you just need to take bus no.1 to the scenic spot directly.
If it's the South Station, you can take a direct bus near the exit to the scenic spot. The ticket fare is around CNY60/person. It takes around 1.5 hours on the way.

Thank you so much Jenny!!! Have a nice day!