High Prefect Castor:
To meet the qualifications to become an Shaman, your level must be at least 20 and you must pass the Test of the Shaman.
I am satisfied with your level, but it seems that you have not passed the Test of the Shaman yet. To take the test, go to Tataru Zu Hestui of the Orc village. He will tell you everything you need to know. After you pass the test, come to me and I will change your profession. Use the Gatekeeper to go to the Orc village.