There are two ways to train in the game. The first is "daily" training, the second is by winning combats. Obviously, the first is easier and more advised in the start
To do so, you must make a subject in the Training Grounds. You then post the date and roll a dice per training.
When you defeat an ennemy, your earn 10xp multiplied by their class rank.
Defeat an Apprentice you earn 10x1 = 10xp
Defeat an Arch Sage you earn 10x5 = 50xp