Buy tickets and join the crowds at a game at Bogyoke Aung San Stadium. If there's nothing scheduled while you're there, you might like to check if they give a tour of the facilities.
When you've finished up at this sporting facility in Yangon Downtown, why not make your way to Shwedagon Pagoda, Sule Pagoda, and Myanmar Plaza? They're not far from Bogyoke Aung San Stadium and also popular with travelers.