Google and vice!
I learned a bit from guides on youtube and from the blender home page (it have plenty
tutorials and vids). Then it was just "try and error", with patience and time.
You need m2mod too if you want to import the model with the armature and animations. The m2mod transforms the m2 into m2i, wich is a format that blender can read if you have the plugin.
You can find that tool in modcraft, or here i guess.
If i have time, i will make a simple guide for making simple animated models with blender for WoW
Regards.