Up to six Wii Remotes and/or four Wii Pro Controllers can work together with the Wii U using either the sensor strip on the Wii U GamePad or the sensor bar.
What to do:
While on the Wii U Menu, press the SYNC Button on the Wii U Console to display the controller pairing screen.
You can also pair controllers from the HOME Menu
2. Press the SYNC button on the console again until the screen shows the controller type you want to pair.
3. Press the SYNC button on the Wii U Pro Controller.
4. Follow the on-screen instructions
5. The Player LED on the controller will light up when the pairing is complete.
The Player LED indicates the player number of the controller currently in use.