Grand Master Tobias:
To become a Shillien Oracle, the appropriate level and token are required. Your level must be at least 20 to qualify to change profession. Also, a token that proves that you passed the Test of the Shillien Oracle is required.
However, it seems your level is not high enough, and you have not yet passed the test. First, raise your level to 20 or higher. To take the Test of the Shillien Oracle, you should visit Magister Sidra of our guild. You can change profession to Shillien Oracle only if you pass her test and bring back the Orb of Abyss as a token.