To train for spells, there are class trainers for any class. In the starting areas, and all capital cities, there are class trainers. Not all cities have all class trainers. When you right click on the trainer, you click "I would like to train", or something like that. At every other level (starting at 2, ending at 61), you can gain new spells from this trainer. It tells you what rank the spell is, what it is, and how much it/that rank will cost. You can also re-spec. These are when you get your talents back, and you can spend them again. At level 40, you can learn to dual-spec. With this, you can learn 2 specs at once. If you want to respec, you can. Switch to your other spec, and then re-spec. Re-speccing will cost more each time that you do it.