Non Jew attendance at Jewish Shabbat service?

How would a non Jew properly go about attending a service? For a church you just show up. But I don’t even go to churches where I am an outsider to the culture such as Orthodox churches or black churches. So I do not know what is even appropriate for going to a Jewish service. My reason for going is to hear the sermon as I agree with Jewish theology more than Christian and want to hear what believers hear