Replacing a Light Fixture

I have 3 wires coming out of my ceiling. Black, Red and White. The previous fixture had 2 wires from the ceiling connecting to one fixture wire and the third ceiling wire was connected to the other fixture wire. The wall switch is a dimmer that has one black wire connected to a red wire and the other black wire is connected to 2 black wires. The switch green ground is not connected. Which 2 wires from the ceiling do I connect together to what color wire on my fixture and which gets connected alone to what fixture wire?