Unlike other Nintendo products, the Wii U console does not come with a Club Nintendo registration card. To register a Wii U console in Club Nintendo, simply link your Nintendo Network ID to your Club Nintendo account. To do this, please follow these steps:
If you are already a Club Nintendo member:

Step 1: Connect your Wii U console to the Internet and perform a system update this will add Nintendo eShop to your Wii U

Step 2: Touch the Nintendo eShop icon on the Wii U Menu or HOME Menu to start Nintendo eShop

Step 3: If you're accessing Nintendo eShop for the first time, you will be prompted to link your Nintendo
Network ID to your Club Nintendo account

Step 4: Alternatively, select "Menu" from within Nintendo eShop, select "Settings / Other" and "Club Nintendo Account", then follow the on-screen steps to perform the link