Purchase tickets and join the crowds at a game at Nuevo Colombino Stadium. If there's nothing on while you're in town, you might like to check if they offer a tour of the facilities.
When you've finished up at this Huelva sporting facility, why not check out Playa Huelva, Punta Almenara, and Huelva City Hall? They're not far from Nuevo Colombino Stadium and also popular with many tourists.