Grand Master Ramos:
To become an Elven Scout, you need the appropriate level and token. Your level must be at least 20 to qualify to change profession. You need a token to prove that you have passed the Test of the Elven Scout, as well.
However, your level is not high enough, and you have not passed the Test of the Elven Scout. First, try to raise your level to 20 or higher. Also, if you want to know more about the Test of the Elven Scout, go to Master Reisa in the town of Gludio. To become an Elven Scout, you must pass her test and bring back her letter of Recommendation.