Here it is, the walkthrough

1. Buy the wand (for those who haven't)
2. Go to Zendar.
3. Talk to the guy in the tower, much of the dialogue is broken, but i used the dialogue files to find out what it was suppose to say.
4. Talk to him about magic.
5. You have now learned the spell Fireball. (there is no visible indication to that, so you will notice it in battle)
6. Go to battle with a few looters (for a start, just for practice)
7. Equip the wand.
8. Press 6, and you should see a message Fire spells
9. Press E, and in the lower left corner the Fireball icon should appear.
10. While the icon is there, left click.
11. The spell should now selected (it will appear in the previously empty box, as seen in the fireball screenshot on page 1
12. Now use the left mouse button to cast the spell

To get other spells, find other mages hidden in towns. I mean really hidden, for one i had to climb on rooftops (like assassins creed) talk to them, maybe do a task, and the spell is yours. The more u use the spells, your magic level will go up and your spells will upgrade automatically.