Using social media to advertise your event is one of the best ways you can advertise your event, there are many benefits of using social media to advertise your event and you are likely to get a much bigger reach than traditional advertising and it can be a fairly inexpensive way to advertise.
The first thing you should do is start posting about your event to get the momentum going. Offer snippets of information on your business page or any groups that allow you too.
Once you have established all of your event details you should now set up your event on Facebook, you should do this by using the events feature on Facebook. Once you have created your event you should share with your current following on your business page, personal and groups that allow it.
Next, you will need to share your event wherever you can. Ask local advertising pages or local media pages such as newspapers or radio pages if you are allowed to share your event on their Facebook page. You should allow yourself enough time to share very frequently to allow more people to see your event.