How to Upgrade Your Account:
You can upgrade your account during the installation process. If you choose to skip the upgrade at that time, have your Authentication Key handy and go to the following web page: http://signup.worldofwarcraft.com
Follow the steps on that page to upgrade your existing World of Warcraft account and recovery options. We strongly recommend that you write down all your security and recovery information for additional reference.
Why You Need Your Authentication Key:
You cannot set up an official World of Warcraft: Wrath of the Lich King account without a valid Blizzard-issued Authentication Key. This means that you will be unable to login and play the game.
For this reason, it is important that you DO NOT throw away or discard your Authentication key. We strongly recommend you make a backup copy of the key somewhere you are certain you will not lose it!
Where to Find Your Authentication Key: Your Authentication Key is located on the front of the CD case. You must have an authentication key to set up your account for World of Warcraft: Wrath of the Lich King. This is what makes your account and copy of the game unique to you.
Creating your character
Creating your character is very easy. From the Create Character screen, select your race and class. These decisions will determine what abilities are available to your character. All of the other options on the character creation screen will help you in customizing your characters appearance in-game, but will not affect your character's abilities or statistics.
Note: Keep in mind that Horde and Alliance characters will not be able to play with each other.
Horde vs. Alliance split
The Horde is at war with the Alliance for the world of Azeroth. Horde and Alliance players are unable to form groups with each other, trade, create guilds together, or even talk to each other. If you have friends you wish to play with, be sure that you select races that are allied with each other. The characters on your account can be of either Horde or Alliance faction, but you and your friends must be of the same faction to play together.
Character customization
You can customize various aspects of your character's appearance. If you prefer, simply click the "Randomize" button to have the game create a random character for you. You can hit this button several times until it creates a character that you like. There will also be ways to further customize your character in the game, both in terms of appearance (such as with weapons and armor) and in terms of attributes and skills your character can learn.