how to host a fitness conference in my local area.

I agree with Tyler Freitag that you should clarify the scope, regularity, idea of the event and some other nuances. I can advise you to look at https://digthesegigs.com/ where people can find tickets at normal prices. Look at the various options for organizing and perhaps find inspiration for yourself. But in any case, start with a clear definition of what people should endure after attending your event.