Light fixture wiring
The green wire coming out of the new fixture, should be connected to the bare copper wire from the ceiling.  There should also be a pigtail from that connection, that connects to the green grounding screw on the strap (metal bit attached to the box).

Then it should be black to black, and white to white. For future reference, you should take photos, draw a diagram, or simply list/label all the wires when you disconnect them from fixtures before you remove them. That way you'll know how it was wired, and can wire it back up the same way.