Purchase tickets to see a game at McHale Park. If there's nothing on while you're in town, you might like to check if there's a tour of the grounds.
If you're planning to stick around a while in Castlebar, McHale Park is a great place to start your exploring. This sporting facility is one of many attractions worth checking out here. TF Royal Theatre and Event Centre, National Museum of Country Life, and Franciscan Monastery are also waiting to be explored nearby.