Purchase tickets to watch a game at Spiroudome. If there's nothing scheduled while you're in the area, you might like to check if they give a tour of the facilities.
You're spoiled for sightseeing choice when visiting Charleroi. Spiroudome is a good place to kick off here, but there are many other interesting sights to experience. City Hall of Charleroi, Stade Velodrome Gilly, and Rive Gauche are near the sporting facility and will round out your day nicely.