Going to court is never easy. I guess that procedure depends on where you are going, I suppose you're going to something equivelant to a crown court that we have over here. Just keep yourself calm, and don't let yourself get intimidated by any of the lawyers, and you'll do fine

You basically wait in a seperate room until you are called, someone will be out to fetch you, then you go into the court room (since he had a gun and could be dangerous, the criminal guy will probably be behind very tough glass or out of any kind of reach), and just answer any of the lawyers questions (that you are allowed to answer anyway).