Buy a ticket and join the crowds at a game at Welford Road Stadium. If there's nothing happening while you're there, you might like to check if the stadium offers a tour of the facilities.
You'll have no end of sightseeing choices when visiting Leicester. Welford Road Stadium is a good place to begin here, but there are lots of other interesting attractions to experience. Leicester Cathedral, Highcross Shopping Centre, and New Walk Museum are near the sporting facility and will round out your day nicely.