First of all, you will need to accept a User Agreement and provide personal information. The information includes providing your birthday, gender, state, time zone, username, password and a valid e-mail address.
Once this is done a confirmation e-mail will be sent the mail address provided. Open this e-mail and click on the link to activate your Nintendo Network ID.
Your username can include numbers, letter, dashes, underscores and periods; as long as it stays between six and 16 characters.
Finally, it is recommended that you update your console as soon as possible. A new update has gone live, and this will let you gain access to more features, including Nintendo’s eShop, Wii U chat and Miiverse.
The Wii U was just recently release in North America and will launch for Europe on November 30.