How do you hook up a second wireless controller to your Xbox 360?

Press the Guide buton in the middle of your controller.

Press the little button on the side of your controller that the triggers are on. I believe it's more to the right.

Press the small button just under the right edge of the disc tray of your xbox

Wait for em to connect to each other and then you're good to go.

Note: If there's already four controllers connected, another controller cannot connect.