Read the volumes of The Schools of Arcane Magic found in Dalaran listed below. You just need to find the books in Dalaran and read them - easy enough, but might take you awhile. The books each have a 3-4 hour spawn time after being read. It is possible for a fake book to spawn so you need to have some patience with this one. Here's a list of the books and their locations:

• The Schools of Arcane Magic - Introduction: 56,46 in Archmage Celindra's room. The book will be on the floor next to the bookshelf.
• The Schools of Arcane Magic - Conjuration: 31,46 in the Violet Citadel. It should be on the bottom shelf of the bookcase on the left side of the room as you enter.
• The Schools of Arcane Magic - Enchantment: 43,47 on the balcony of the cloth armor shop.
• The Schools of Arcane Magic - Necromancy: 46,39 upstairs of the Legerdemain Lounge inn. It should be the lonesome book on the bookcase.
• The Schools of Arcane Magic - Abjuration: 52,55 in the Dalaran Visitor Center. It will be on the floor near the two bookshelves.
• The Schools of Arcane Magic - Divination: 26,51 in the Violet Citadel. The book should be to the left of the Caverns of Time portal.
• The Schools of Arcane Magic - Illusion: 64,52 in the Violet Hold (not inside the instance!). It should be on top of a crate in the corner of the room.
• The Schools of Arcane Magic - Transmutation: 47,39 on the first floor of The Legerdemain Lounge. Should be on an empty bookshelf.

Reading these books will also grant you access to the pet Kirin Tor Familiar!