If my daughter's fathers is $2300 behind in child support and refuses to pay, how do I file contempt of court?

You can file either through an attorney, yourself, or your local child support enforcement office.  I will give you a link to the booklet in the MAryland Court system that will help you through the process.  You should consider having the money automatically garnished from his pay every week.  Good luck.

http://www.courts.state.md.us/family/forms/supportcontempt.pdf