You'll need to reach level 125 First Aid first, and head out to the respective place listed below.

Alliance

1. Alliance should head out to Stromgarde in Arathi Highlands and find Deneb Walker (27, 58 on the right side of the keep). Purchase the book Expert First Aid - Under Wraps (cost is 1G), Manual: Heavy Silk Bandage (cost is 22 Silver) and Manual: Mageweave Bandage (cost is 50 Silver).

Horde

1. Horde should head out to Brakenwall Village in Dustwallow Marsh and find Balai Lok'Wein. She's located at 36, 30 just behind 3 ogres! Speak with her to purchase Expert First Aid - Under Wraps (cost is 1G), Manual: Heavy Silk Bandage (cost is 22 Silver) and Manual: Mageweave Bandage (cost is 50 Silver).

: Blue post on patch 3.1 states - "You no longer need to learn cooking from books. The trainers have finally done their reading and are able to teach you the same thing."