How do I get my 2nd class?

You will need to be level 40 to get your 2nd class. You can find the NPC for Warrior in the Spiritual Church in Meteor Pit, the one for Machinist is in the Weapon Shop also in Meteor Pit, for a Mage you need to go to the Wizard Cave in Thunder Hill, and for a Shaman you need to find the NPC in the Crystal Room which is also in Thunder Hill.