The white men gamble in it. You could say it is used as a casino. This probably begs the question, with so many of their own churches in town (the Baptists play the Methodists in football), why don't they use their own houses of worship? The book never tells us, but that is the beauty of Harper Lee's work. She leads us as a reading audience to draw our own conclusions about what happens in the text. So, if you are answering a question for class or having to analyze what goes on in the church building during the week, draw a conclusion about what you know now. What does that show further about the society and race issues in Maycomb?
Hope that helps.