I need information on how to file a Libel / Slander case. A Previous contractor that was let go posted on the City Facebook Page, seen by over 17,000

A contractor that was let go by a company posted slanderous / libel remarks about myself. I am a General Manager at a rental company. This post was done on Facebook City Group Page with over 17,000 local subscribers, wher a lot of property owners I deal with and staff saw the post, where this contractor called me a f^^^& racist bastard etc, This caused several high ranking members in the area to see this false remarks as well as several staff members. Printouts of these remarks were made. The contractor is white, and I am also white - Thus no racial difference.