Complete the tutorial, create an in-game name and you are ready to play!
The Mage will be your starting class. The other classes can be unlocked by reaching level 20 with each previous class.
It is recommended that you unlock and try out all of the classes, to find your favorite.
When you've made your Mage, get to around level 15, then head to the Godlands (gray, stone colored tiles) to try to get better gear for your character.
If you are able to stay alive for a while once hitting level 20 and would like to advance yourself, proceed to the guide: Beyond Level 20.