Put it on auto and enjoy the wedding.
Ugh. Auto mode and flash is only good for people trying to stand still because it'll just about always use 1/60 f4. I'm not sure if it will allow a flash in sports mode if you're trying to capture dancing.
Indoor flash photography take a while to learn. Auto mode and flash gets you, well P&S/auto looking snapshots.
I'm sorry but you cannot learn how to use a flash with the camera in M mode in one day for an important event like a wedding. You should have been asking 1 month ago.



