You have to purchase a book called something like "Expert First Aid - Under Wraps". Go to the column on the left on this page and go down to 'trade skills' and 'list of trainers'. It will tell you the name and location of the npc for Alliance and Horde who sell the book.
The book can also be found in the auctin house as well for an inflated price.
Hope that helped.
Some people are like Slinkies. They aren't really good for anything, but you can't help but smile when you see one tumble down the stairs.