How to choose a second class?

[Rusya]

I play a swordsman for 15lvl class chose Blossom Blader raised his 30lvl class and I don't know how to choose the next class. Help me please.

[KakSource]

You have to have max level in class i think is 45-40 something like that then a huge button in the right side of the screen will appear that says: "Advancement" until so you keep levelin' till you get it

[Ellador]

The base classes (swordy, mage, archer, cleric and scout) only need 15 class levels, but the others have 45 class levels.
In your case, you need to be Blossom Blader class level 45 to select a new class, and when you hit it, you will a notification with a huge "ADVANCEMENT" button you surely will notice.