Purchase tickets and join the fans at a game at Fernando Buesa Arena. If there's nothing on while you're in town, you might like to check if the stadium offers a guided tour of the facilities.
When you've finished at this Vitoria-Gasteiz sporting facility, why not make your way to Mendizorroza Stadium, Virgen Blanca Square, and Cathedral of Santa Maria de Vitoria? They're near Fernando Buesa Arena and also a favorite with many tourists.